The last IGF finalist game I played seemed like an interesting concept but was ultimately boring.
Oh, it's actually a fun game, not just conceptually good. Everyone I know who's played it seems to get fairly addicted. Short game (18+ levels), but lots of replayability. It's basically a platformer that doesn't have any platforms... you're a circus acrobat swinging around on trapeze-like things instead, performing tricks and stunts to impress the audience and get through the arena. It starts off simply, but gets really involved and complex after a while. Plus the art and music are fantastic. And there's an easy-to-use map editor for making custom maps. You can see Destructoid's review of it here. It got the same numerical rating score as Gears of War 2, if that's any help. :) And it was also voted best XNA game of 2008.
You can see the trailer on Youtube here.