I've been thinking about Quicken yesterday night. One or two in a deck seems very underwhelming to me. If you play Quicken, you should have it as a 4-of to gain anything out of it. Having just one is randomly good, but randomly just as bad, since you can never rely on having it when you want it and when it shows up, you'll have to shape your play around it. No, what I like about Quicken is that it allows you to build a 56-card deck and has a useful effect besides just cantripping. This useful effect is better than that of other instant one-mana cantrips (Mental Note) unless you run Threshold.
Of course, Quicken (as has been pointed out
here, for example) requires a lot more mana to use your sorceries instantly. However, since this will be end of turn anyway, you need to be aware of only your opponent's instants or just have FoW as backup. This is mitigated by the sheer power of end-of-turn sorceries, though. Think Demonic Tutor, Burning Wish, Time Walk. All of them are strong. Tapping one more mana is not exactly welcome. But you don't have to.
What Quicken does is to make people think "oooh, now I have to wait for Quicken to show up to play my sorcery eot". That is unnecessary. If you view Quicken just as a cantrip that gets you to your winning card faster, cycling through your deck, that is incidentally good when you also have a sorcery, it becomes easier to use and understand. (Also, you might always draw a sorcery off the Quicken and can then play it...)
The deck I can't really see Quicken in is straight Gifts. That deck already needs a lot of mana and has no space left to fit in Quicken. Also, the crucial sorceries have to played early (Merchant Scroll) without wating for another blue source and the Quicken doesn't help Will in Gifts either, because you cannot go off at instant speed anyway. What I *can* picture Quicken in is TPS, if just for eot Draw-7's. The cantrip also helps TPS much more than it does Gifts, since TPS has arguably the better topdecks.
The deck I see Quicken in would be a Tinker deck that tries to find the 2U sorcery as fast as possible. The deck could forego the "fancyness" of Gifts and just use Tutors and draw to get to the Tinker asap. It could conveivably incorporate a Gifts framework, with maybe two Gifts Ungiven and Recoup because it would be stupid not to use it, but that could be the backup plan (and it does not necessarily have to). The core of a Quicken-Tinker-deck might look like:
4 Quicken
1 Tinker
1 Demonic Tutor
1 Vampiric Tutor
1 Personal Tutor
1 Mystical Tutor
The draw part of the deck might even be complemented with other cantrips besides Quicken, for no other reason than just to cycle through your deck asap. Green as tertiary color for Quirion Dryad might even make sense; in fact, Quicken and Gro seem like a natural fit. I don't have a deck ready to follow up on that idea, but I think what's most important is that Quicken shouldn't just be stuffed into a regular deck. Thinking what the card does and how you can help it along (or it can help you along) is more effective. That and looking at existing decks naturally leads to Tinker-Gro: The cantrip aspect of Quicken points to Gro, the second effect of Quicken points to Tinker (or TPS, but that's different because Quicken actually helps that already existing deck).
Dozer