I'm happy to see somebody playing ELVES! in today's metagame. With Mental Misstep floating around and Workshop-based decks so strong, ELVES! probably isn't the optimal choice. However, it may depend on your metagame. I'm 95% sure all of the good players in my metagame (NEPA, New York, NJ) will always be properly prepared to combat my little green men. I commend you on your bravery.
I'm going to share some of my thoughts on your build, although I'm hesitant to do so without seeing your sideboard plan. The sideboard is extremely important to the ELVES! deck. Could you share yours when you have the chance? I reserve the right to change some of my comments once you've posted it.

For the record, there's an excellent discussion about ELVES! in this post:
http://www.themanadrain.com/index.php?topic=41147.90 . I'll probably end up repeating myself from there, but here goes.
4 Birchlore Rangers
4 Wirewood Symbiote
4 Quirion Ranger
4 Summoner's Pact
4 Glimpse of Nature
4 Skullclamp
4 Llanowar Elves
4 Fyndhorn Elves
4 Heritage Druid
4 Nettle Sentinel
1 Emrakul, the Aeons Torn
4 Wooded Foothills
6 Forest
3 Arbor Elf
4 Windswept Heath
1 Viridian Shaman
1 Elvish Visionary
Yup. This is a powerful one. Obviously not my design at all. Arbor elf is a clear addition as the 1 drop mana elves allow for t2 kills and resilience against spheres.
What you don't see:
Cavern of souls. Unneeded against control. If they are countering your creatures, you will be fine. They have 10 counters max. You have 31 creatures. It is good against chalice, but not as good as arbor elf is vs the field (arbor elf is a clear nonbo with cavern).
Grapeshot. Not as good as emrakul. Emrakul is invulnerable to hate. Stifle buys them a turn. Mindbreak trap still gets you an extra turn in which you attack for approx. 1 million. And emrakul allows monogreen. Even corner cases like ensnaring bridge can be circumvented by your army of 1/1s.
2cc mana elves.not worth the mana investment. The singleton visionary is a tutor target to combo with wirewood symbiote to draw into some gas when the game has stalled.
Shop is still your worst match up but better now that people are moving away from phyrexian revoker. You do have the mainboard combo of wirewood + shaman which wins the game without you having to even come close to comboing out.
To wrap up this short post, elves is well positioned especially as people use combo hate like thalia and flusterstorm, which this deck shrugs at. Most importantly, it is a blast to play/
There are many things that I like about your list. First, the Arbor Elf creatures sitting in as Llanowar 9 - 11 are very interesting; I agree that they are probably one of the strongest plays in the deck. They certainly aren't as strong as the other 8, but they do help you get around Spheres and start the combo with Quirion Ranger (sort of) in a pinch.
I agree that Grapeshot doesn't really have a place in the deck. Emerakul has the benefit of being colorless and has a built in time walk. However, in my opinion, his biggest advantage is that he is uncounterable and that he ignores Storm hate; but more on that later. On the other hand, you'd be suprised about how often he can float to the bottom of the deck, both drawing out the game and risking the chance for a loss by decking.
I really like the 1 x Elvish Visionary, as well; especially with 4 x Wirewood Symbiote. It allows you to play catch up if an opposing character counters your draw spells, and it also helps in the attrition war against Workshops.
That said, I think that the deck has some holes that can be filled.
Before I get into the individual card choices, let me post the list that I currently have together:
Ryan Fisher's ELVES! (6/6/2012)
4 x Llanowar Elves
4 x Fyndhorn Elves
3 x Birchlore Rangers
4 x Heritage Druid
4 x Nettle Sentinel
4 x Priest of Titania
4 x Quirion Ranger
3 x Wirewood Symbiote
1 x Regal Force
1 x Emerakul, the Aeons Torn
1 x Viridian Shaman
4 x Glimpse of Nature
4 x Skullclamp
3 x Summoner's Pact
1 x Black Lotus
1 x Mox Emerald
3 x Cavern of Souls
5 x Forest
2 x Wooded Foothills
2 x Verdant Catacombs
1 x Windswept Heath
1 x Misty Rainforest
Sideboard:
2 x Gleeful Sabotage
1 x Seeds of Innocence
3 x Viridian Shaman
1 x Wirewood Symbiote
2 x Xantid Swarm
2 x Green Sun's Zenith
4 x Gralfdigger's Cage
For the record, that's 4 cards in against Big Blue / Blue Control, 4 in against Dredge, 6 in against Oath, and a whopping 9 in against Mishra and his ilk. Probably 3 in against Fish as well.
Now that you've seen my list, here's some of the parts of your list I don't particularly like.
1) Now You're Playing with Power
You make several interesting points about Black Lotus and Mox Emerald, but I think you may undervalue the speed and tempo that they bring to the deck. You make a pretty strong point about not being able to keep a hand with only Mox Emerald or Black Lotus. If one of them is your only mana source, and your opponent playing blue counters it, then you're in trouble. Especailly Lotus -- people will usually let the mox through. On the draw, decks that play Chalice of the void can randomly blow them out (although if they're playing Chalice at 0 against this deck, they're probably doing something wrong.) I suppose they can get blown out to Null Rod / Steel Sabotage / Spell Pierce as well. These are all good points.
In my testing, however, I have found that the extra mana can be a godsend against random blue decks mid-combo if we start to stall. I can't tell you how many times I'll start combo-ing and hit a string of Glimpses or Clamps, where having the extra playable mana source helps the combo keep going. This has always been a super tight combo deck, and sometimes you need to cast a creature to be able to keep the chain going, but end up stuck with a land and a Glimpse in your hand. If you're strangled on mana and creatures, hitting a land off the top will mean you lose. If you have an Emerald to plop down that second Glimpse, it can be the difference between living and dying.
Also, the advantage that these cards grant you against Workshop-based decks on the play cannot be understated. You make a wonderful point about the strength of Wirewood Symbiote in this match-up, but against this type of deck, mana acceleration is the only game you have to play. Forest -> Emerald -> Elf Elf is absurdly strong against Workshop decks. Not only CAN they outpace your Forest -- > Llanowar / Fyndhorn / Arbor Elf, they probably will. Sphere or Resistance and Chalice of the Void are not your friend.
Also, Lotus will randomly win you the game on Turn 1 -- especially with your current set-up -- and that's always fun. I would run at LEAST 15 dedicated, non-one-drop mana sources in the deck (You currently hold 14), but two will always be Mox Emerald and Black Lotus.
2) Mishra's Workshop -- the Boogeyman.
I'm glad that you recognize that Shops is this deck's worst match-up, and that if you think you will face several Workshop decks, you probably shouldn't play this deck. You're probably right. However, I think we might have access to the right set of tools to combat this menace right now. I also think that there is a build that can balance the Control / Workshop match-up to do fairly well, but I don't think that your build is quite right for the task. Once again, I can't be sure without seeing your sideboard--I pack 8-10 cards against Mishra and his ilk, with a main deck designed to support wrecking Shops--but often I find it's still not enough. Workshop-based decks are just too fast and too resilient.
I must also use another disclaimer: I routinely play some of the best Workshop pilots in the world. The deck keeps me up at night, I fear it so much. Workshop's strength and prevalence in the metagame is the ONLY thing that keeps me off playing this deck on a regular basis. The match-up is abysmal. It doesn't matter if I can dodge shops throughout the entire tournament and make Top 8 just to get crushed by shops if they make Top 8. I cannot count on blue players knocking out all the Shops.
The standard Workshop deck runs at LEAST Five sphere effects that we should fear: Lodestone Golem and Trinishpere. Most also run 4 x Chalice of the Void, which will annihilate your deck more often than not. Having only one drops makes the deck curve out like a dream, but it also makes it extremely vulnerable to Chalice. Viridian Shaman and Symbiote can do great things, but not if you can't cast or find them. Your 11 one-mana, mana producing helps may help you curve out. But even if you're on the play, if they go Turn 1 Chalice at 1 and Sphere of Resistance, you're probably going to lose. They can mulligan better than you, play just as many four-ofs, and will draw better mana than you on a regular basis. 14 x Forest seems like a good number, but when they outpace your mana sources 3-1, it's an uphill battle no matter what. I count having a resilience to Workshop decks as the most important thing in the Elf deck -- even over dredge. This will color the rest of my choices.
2. a. Power (See above)
2. b. Priest of Titania
You make great points about Priest of Titania. If we don't see her on Turn One or Two, we very rarely want to see her at all. She clogs up our hand, clogs up our combo, and probably grants a Time Walk against a blue player if -- and when -- the blue player counters her. On the other hand, you made the point that if the blue player counters her that we're in good shape, so it's not all bad.
Although she harms the explosiveness of the deck, she helps the deck in several important ways. First and foremost, she can be amazing against Workshops. If we're on the play and drop Forest --> Llanowar Elf, and we have another non-creature mana source and Priest in our hand, we're in pretty good shape. If the Shop player plays Chalice at 1, we don't care. If he plays Sphere / Lodestone Golem, we don't care. If he plays BOTH, we still don't really care. Racing mana against Shops is the most important thing you can do, because Green artifact hate -- despite green being one of the best colors for it -- is usually too expensive to be effective, or costs 1. Priest helps cast Visionary to out-draw the Shop player, and once Viridian Shaman + Symbiote hit the table, like you said, it's usually good game from there. Priest of Titania also plays nicely with untap effects to blank Tangle Wire, allowing us to cast good sorcery-speed removal, such as Viridian Shaman, Gleeful Sabotage, or Seeds of Innocence.
Priest of Titania helps the deck in other, more subtle ways as well. In my experience, Summoner's Pact is a dead card more than it's useful. Summoner's Pact is only useful against control deck when: one, you're probably already winning; two, you have more than four lands / mana on board; and three, when you need to get a utility creature. Priest helps smooth the Pact out in several of these ways. As xoumen pointed out, using Pact - Priest to ramp mana if we're down on cards isn't a terrible idea, especially if it helps turns that include multiple Elvish Visionaries, Regal Force, or even Emrakul. One of the best things about Priest is her ability to hard cast Emerakul using your 8 untap effects -- especially in a heavy control or Shop matchup, it really helps to be able to count on hardcasting Emerakul. You can also dodge Storm hate this way, which I mentioned earlier. The Priest + Emerakul strategy is what makes Emerakul so much better than Grapeshot, in my opinion.
3) Regal Force
I can see why you're reticent to play Regal Force in your build. You're on the super-fast, super-curve combo build, and Regal Force is probably clunkier more times than not. I'm interested in testing to see if Elvish Visionary + 4 Symbiote is better than having a Regal Force to tutor for, but for now I remain skeptical. Summoner's Pact is most worth the risk when you have a big, swingy, and powerful creature to cast off it, and I think Regal Force is probably the best one. Even without the Priests, I think I would support xouman's choice of playing Regal Force for that reason.
4) Cavern of Souls.
You make some great points about Cavern of Souls, and I think I need to test it much, much, much more to test its validity. Filtering Cavern through the Workshop lens, it has amazing potential. The ability to cast mana dorks through Chalice of the Void may outright win us many, games. I don't fear Spheres as much as Chalice, and forcing one or two additional little guys in there can make all the difference, especially if they're self-sufficient mana dorks. However, the fact that it's also a non-forest, non-basic is a huge detractor. If they have a chance to Wasteland or Stripmine a Cavern before we have two or three turns to make great use of it, we're probably going to lose. Against Workshops, it's probably better as a sideboard choice in your deck than my with my changes, because your reliance on one drops hurts you just a bit more than if you were playing Priest / fast mana. On the other hand, it can also blank your Arbor Elves. You may be dismissing this card too quickly, or you might be completely right. I'm honestly not sure.
In the control match-up, I think this is still a good card to play for a few reasons. First, it helps you sneak past Mental Misstep. I have always said that a good player will let the creatures resolve and counter the draw spells -- as people have mentioned -- but I'm not sure that's always the case. Sometimes countering the creature is the right call, in the case of a Heritage Druid, Nettle Sentinel, or Quirion Ranger, especially in the early game after you've cast a Glimpse. Remember that they have more counters than you do draw spells, and probably more ways to find counters. If you're low on mana / game state / cards, it can be correct to counter a creature of the Glimpse. Most control decks with a combo finish -- even one as mundane as Time Vault / Key or Blightsteel -- have better ways to find those cards in mid-game to late-game. It creates a powerful dichotomy, where on the one hand we need to beat them before they can use their vastly superior tools to beat us, but we don't want to lose our steam by going all out. Therefore, in the face of an early Glimpse, it might be more relevant to counter the creature of the draw. (Especially if you can't sandbag a Lotus, Emerald, or Priest). Cavern can force them to counter what you want them to counter, and that can be a strong advantage. Also, a hand with multiple mana sources, including Cavern, can make sideboard games interesting if you go Cavern --> "Insect" ---> Uncounterable Xantid Swarm.
Sorry for the long read, but I think about the theory behind the Elf deck too much. The problem with ELVES! right now (and the problem with it since around the time Lodestone Golem was printed) is that it doesn't do anything particularly well.
Pro: It combos very quickly with a ton of four-ofs.
Con: It sacrifices disruption and tutoring to do so. If the plan is to meaningfully interact with other decks, TPS, Gush-Tendrills, or Drain-Tendrills is probably better. If you want balls-to-the-wall combo, Belcher is much faster. Dredge can play either of those two roles better, as well.
Pro: It combos with a beat-down option behind it. A one-two punch.
Cons: 1) The beatdown express is very slow, especially if you have to try to combo as well.
2) All the creatures are so small that Pyroclasm, Massacre, and the like all hose it beyond recovery. Blue decks will probably have a cheap, efficient board sweeper to play against Fishy-type decks, and several tutors to find it.
3) As discussed above, no disruption to help the Beatdown plan. Goblins and most Fishy decks do this job much better.
Con: It likely outright loses to Oath if the opponent lands an early Oath activation and gets Iona, Griselbrand, or Rune-Scarred Demon.
Con: It rolls over to Shops if on the draw at all. It has a very small percentage Game 1 outside of a blow out Lotus-Land-Glimpse on the play. It almost requires 8-10 dedicated sideboard slots, and still probably has below a 50% chance even on the play.
Con: If it prepares for all the other decks, it probably outright loses to Dredge.
Pro: It has a good chance of beating a Fishy deck if it can get away with hardcasting Emerakul. It can win the attrition war with Wirewood Symbiote by himself, or with Elvish Visionary.
In closing, your decision to (apparently) go straight combo may be the best way to play the deck right now, but I think it's just way too fragile to be a good choice unless you can GUARANTEE that Workshops will not show up. It can't adequately prepare for a diverse field like Shops, Big Blue, and Dredge can, and it's way too inconsistent to win reliably. My version probably has the best chance to stand up against a normal competitive metagame, but the chances are probably not that much better.
That said, I hope you continue to play ELVES! and that it does well for you. I play a deck with Elf creatures in basically every format, so I know how much fun they can be. In Vintage, however, where the costs are so high, I'm not comfortable playing a deck that doesn't stand a good chance against the average field without some super luck. We have a saying around here that goes, "I'd rather be lucky than good." I agree with that sentiment, but I cannot rely on it. I guess I'm too much of a coward to play ELVES!, unless it's Christmas and I can wear a Santa hat.