Performance Scaling XP to Vista

On average with the Geforce GTX 280 you lose -1.6% by switching to Vista 64-bit, so in short: same performance and no loss!

The Radeon HD 4870 X2 does even better, if we leave out the numbers of Stalker and Tomb Raider (as Crossfire failed to run properly under XP) we see a +5.8% boost in average FPS going from XP to Vista. If we add the two game titles and let them enjoy CF-scaling the number jumps up to +27.7%!
This is laughable because it's such poor logic. What you'd want is that there be NO difference between XP and Vista. They paint the "gains" in Vista as a plus.. when in fact it's just a testament to poor ATI XP performance...