Over at Quakecon Ian Cabrtosr McNaughton released Catalyst 9.8 drivers. With this driver, you should see significant performance increases on AMD platforms.
These improvements are more platform related you will see gains of up to 50% in some titles (like Far Cry 2) when using a CrossFire solution with 4870 X2 or other 4xxx series in resolutions 16x10 and higher youll see these gains mostly in CPU-bound situations. You will also see significant improvements in titles like HAWX, Crysis, Company of Heroes and World in Conflict.
We have a discussion thread open on these drivers right here.
Have you read Guru3D's Windows 7 vs Vista VGA game performance article already ?