I have a quad core system with a lowly Radeon 2900, and the game runs nicely with everything on very high. I run a Windows XP system, but I downloaded a patch that makes the high setting very high, and the game is just gorgeus!
I also agree with others, the game is great until you start fighting aliens in a zero gravity environment. So many 1st person shooters do that, like the 1st Half Life, and the dissapointing treck through Zen. Killing humans(or zombies) just can't be beat.
