So I just got a ATI 5850 here at work..

Machine specs:

Core 2 duo (dual core 2.66ghz)
2 GIG of DDR2 800
Windows 7 RTM
Latest Catalysts
ATI 5850 (1gb)
Corsair 450W PSU

So to test it out we put the crysis demo on - the original one from way back when. We couldn't get fullscreen working properly but in WINDOWED mode we:

Set AA to 2X
Set all graphics settings to VERY HIGH
Res to 1280x1024

Non scientific result - it runs as smooth as butter - i'm utterly impressed, lord knows the '70 must be a monster!

[in case your wondering we're actually interested in developing a new product for DX11 so hence this card and we're actually be using it for scientific software not gaming. Mostly.]