Until ATI sort out their driver support issues (Vista ,Vista 64) then the performance of this new product is entirely academic. There are so many Dell Studio XPS owners with a 4850 experiencing a:

"Atikmdag has stopped responding and has successfully recovered "

and Dell have failed to address the issue over the last 6 months. I'm not sure how much it is costing Dell, many new units are going back and turning up in the Outlet store. There is no resolution yet - however, turning off the Aero interface or un-installing the ATI Catalyst software seems to solve it. However, if you paid good money for Vista Ultimate, it's not exactly satisfactory to turn off the pretty features of Vista... besides, what other software might cause it to break?

ATI - spend more effort on sorting out the software, hardware specs are OK but worthless on their own...