Ephraim:
I'll look at the Curio. It doesn't seem like it does enough by itself, but I could be wrong - bouncing the enchantments would certainly be very powerful. I know what you mean about cards stealing the limelight - when testing a new casual deck which does something cool I have to mentally separate out the wins where I just curve out and win with utility creature beatdown from the wins where I do the deck's trick.
Simic Guildmage is an idea I've had too - it probably has less raw power, but it's more synergetic with everything else. It's also an easy-to-cast bear, so it's automatically pretty good

Moldervine is an idea I like. Getting good cards into grave can sometimes be a problem, so dredge could be the answer I'm looking for. At the moment Mythic Proportions is like a tutorable 'help' button which I get when I need a fast clock as opposed to genuine board control, but Moldervine would work differently. I'll look into it.
Another unrelated deck: I posted a
thread on this deck ages ago, but noone replied. I'll give it another try here, because it's quite an interesting deck which is pretty strange to play. I've made quite a lot of changes since the last incarnation, mainly centred around trying to fix my almost total lack of disruption. U/G is never going to have good removal, but without some kind of way of stopping my opponen't plans I am very vulnerable.
// Lands
4 Tropical Island
1 Okina, Temple to the Grandfathers
5 Island
2 Flooded Strand
2 Windswept Heath
6 Forest
4 Simic Growth Chamber
// Creatures
3 Meloku the Clouded Mirror
4 Yavimaya Elder
4 Sakura-Tribe Scout
2 Budoka Gardener--Dokai, Weaver of Life
4 Vinelasher Kudzu
2 Soratami Cloudskater
// Spells
2 Rending Vines
4 Exploration
4 Counterspell
3 Gush
4 Mana Breach
Exploration makes me quite a lot more explosive, and obviously more ways to put lots of lands into play makes the the various tricks quite a lot more powerful. After a bit of testing, I think I've found the point where I have the right amount of cards which put extra lands into play - if I go up to 4 Gardeners I tend to have too many land players and not enough stuff to do with the land.
The Simic Bounceland is an obvious addition - extra excuses to get lands into and out of play are always good.
Rending Vines is beginning to look a bit meh. My hand is not always as full at is might be, perhaps Naturalize might be better here.
Mana Breach can be pretty crushing to an unprepared opponent. It can gain fantastic amounts of time in the medium term by slowing the opponent down at every drop. Obviously it's best against slower opponents, but it never seems to be really awful except when I topdeck it looking for an out. In multiples it can be crushing. I also looked at Overburden and Storm Cauldron when I made the choice, but my intuition is that Breach is the best option. I'll certainly try the Cauldron out in the future, just to see what happens, but probably not Overburden. It just seems a lot less powerful.
EDIT:
Storm Cauldron is sooo much fun, although I'm still not sure if Mana Breach isn't better. In my Storm Cauldron version I've gone up to the full 12 'Explorations' and added Flooded Shoreline for a better removal spell.
Current build:
// Lands
4 Tropical Island
1 Okina, Temple to the Grandfathers
6 Island
2 Flooded Strand
2 Windswept Heath
5 Forest
4 Simic Growth Chamber
// Creatures
3 Meloku the Clouded Mirror
4 Yavimaya Elder
4 Sakura-Tribe Scout
4 Budoka Gardener--Dokai, Weaver of Life
4 Vinelasher Kudzu
// Spells
4 Exploration
4 Gush
3 Storm Cauldron
3 Counterspell
3 Flooded Shoreline