Combo with cards to give other players as many turns as possible.

Or Timesifter and win :)

pretty cool, if narrow- maybe put on a creature.

You know, Rudyard, that's an interesting thought process. Personally, I think I'd advise enchantment over creature because it is very narrow. You don't want people putting this in their decks, unless they plan to use it... there's nothing more frustrating then having an ability that never does anything, and tacking this ability on, say, a 2/2 flyer, makes it a bad Wind Drake as opposed to a funky combo card. If the ability was narrow, but came up more often, like with Aven Mindcensor or with Aether Sting, I'd be all like "Hell yeah, that should be a creature."