Tom's Hardware tested 10 games under Windows 8
If you're a Tom's Hardware reader, I'm willing to bet you've endured your share of fresh Windows installations, perhaps even dating as far back as 1985 and Windows 1.0. This one, like those before, will give us new features. We'll love some of them, and we'll hate others. Things we've used for years will break, and other things we've needed add-on driver packages for in the past will work right out of the box. Certain capabilities have the potential to improve performance, and more overhead elsewhere will gnaw away at it.Windows 8 Versus Windows 7: Game Performance, Benchmarked
Really, we don't expect to see gaming performance change in the move from Windows 7 to Windows 8. AMD Zoomeven let us know prior to the FX-8350 launch that a properly patched Windows 7 machine shouldn't behave any differently from one with Windows 8 on it (that's why you didn't see us include Windows 8 numbers). Companies like AMD and Nvidia have had plenty of time for driver development, and proper support for modern graphics cards was in place on Microsoft's launch day. For the most part, once you fire up your favorite game, your experience should be pretty similar.