WTF. I see end user reviews like this and it leaves me scratching my head. How could [H]'s review be so completely off?
http://www.nvnews.net/vbulletin/showthread.php?p=1265358#post1265358
I would guess, and it is just a guess, that they weren't running with HDR+AA on. From what I've read, you need to enable AA outside of the game if you're planning on running HDR as well. So max ingame settings may not be taking AA in to consideration. (Which is where the 2900 takes its biggest hit.)
I've also read a few things about the latest drivers having some problems enabling HDR + AA, but I'm not 100% sure on that.