Most fun I have had gaming in 5 years.
I gave this a try because I wanted a new game to mess around with and for only $30 from xbox live, it seemed like it might be enjoyable.
This game is an absolute BLAST. I can't remember having THIS much fun with a game. The gameplay is tight, the weapons are awesome, the story is good, the environments are varied, the graphics are fantastic (looks this good on a 360? really?), the jokes are freaking hilarious. The combat is a blast when you add in leashing, slides, and kicks. It's everything Dark Messiah of Might and Magic tried to be and so much more.
Ok so it's not PERFECT... no game is (sniping slow-mo is too hard to pull off headshots with, one of the characters I would have love to have partnered with is killed off early on, etc). But these are so minor they are barely worth mentioning.
You could spend $60 on many games and not enjoy this one. This is one of the few games I would recommend to anyone who enjoys FPS's, regardless of price.