There's a free demo on XBL for it.
I really don't like the game.
I was hoping because of all the powers you can have, it would be a fun FPS with a lot of different things you can do. Well, I was half right...there's a lot of different things you can do. Wasn't fun to me though.
Free demo...can't beat that. Definitely try the demo first and play through the tutorial.
I believe it's a multiplayer only shooter - keep that in mind, especially if you're not going to pay for Xbox Live Gold because then you'd be tethered to local/splitscreen play only.
I think there's much better shooters out there for the money, including Bioshock which comes out the 17th I believe.