http://xbitlabs.com/articles/video/display/vista-performance-preview_13.html said:
Even without the results of the gaming tests it is clear that Windows Vista Beta 2 is too “raw” a product to be used for everyday activities. Well, its Beta status doesn’t promise anything. The problems in the new operating system are quite expectable at the current stage of its development, but this is only a temporary thing. Bugs will be eliminated, stability will be raised to the necessary level, and the hardware requirements will become more modest than today when a lot of OS components aren’t yet polished off.
Windows Vista Beta 2 can’t be used for playing games because it is just incompatible with many titles and leads to a considerable performance hit in others. This is at least true for the currently available beta version of ATI’s graphics card driver. Windows Vista allows using the ordinary driver, written in the Windows XP framework (XPDM), but that driver does not have even the basic support for WGF and does not allow using such a key innovation of Vista as the Aero interface. It means that gaming tests in Windows Vista with old drivers wouldn’t be adequate.
By the time the final version of Windows Vista is released, most of the compatibility issues will have been corrected and new drivers will have been written to solve the problem with performance in games. We will see all this in the future, perhaps not a very distant future. Beta versions of Windows Vista suit only for us to become a little familiar with Microsoft’s new operating system. And we shouldn’t fall into the mistake of making any final conclusions out of this preliminary experience. As soon as games that demand WGF support to run appear, the transition of gaming platforms to Windows Vista will be inevitable. But so far, Windows XP is the main OS for gaming platforms and will remain such for quite a long while yet.