Sadly, I do not have a 360 (read: YET) but my friend does and it is an awesome game. Not a perfect game (keep in mind that I don't believe they've ever made a perfect FPS game), but it's definitely one of the better games out there (as far as new games go).
I think Armake put it best when he said there are some flaws (online MPers acting like morons, over-used blur motion to make the graphics look more next-gen, level barriers, etc...), but the game is still great and definitely worth checking out. If for no other reason than to shoot a bunch of aliens.
Story-wise, if you liked Xenosaga, you'll probably like this. I wouldn't say it's as 'epic' as Xenosaga, but since FPS games are more about shooting stuff than big LOTR-caliber stories, it's still nice to have a good deal of cinematic moments in a game like this.