I have the 8800 GTS 640mb I put in my new machine.
They are beasts but there are issues with the new nvidia drivers for them there is only a choice of two (unless they have released another set in the last 2 weeks) I finally got AH running to a decent degree @ 1600 x 1000 on my widescreen monitor Hi res pack. Its cranked up to the max and everything is solid.
Every now and again My gfx will go patchy and I have to alt + tab and let the game reload the gfx whilst on autopilot. I put this down to either AH being old or the drivers being crappy.
In other games all I can say is wow!
Bruv
~S~