I'm running a newish-midrange 1GB Radeon 5850 (backed up by an i7 930 and 6GB DDR3) and the game runs great, solidly 40+ FPS on Ultra and just gorgeous. It's not just the technical aspect of the graphics, though, it's the overarching art style and the shocking lack of glitches. That last point is really a big one: there's no textures sticking through other textures, flashing, weird field effects, obvious banding or grandients, or any of the other things I'd just come to accept as part and parcel of current graphics, and that consistency combined with high-quality assets and overall direction make amazing graphics unobtrusive. Unobtrusive is really the ultimate goal in visual fidelity: make the imagery so good that it's the character, story, plot, game mechanics, and everything else that draw you in, and that's because what you're seeing isn't constantly jolting your brain with "This is fake!" warnings. Not to say that they always get away with it, but it's a big enough leap that everything else will look that bit duller.