Microsoft is reportedly telling it’s gaming industry associates that games will run 10-15% slower on their new operating system due to the new GUI implemented.
Vista’s new 3D desktop will constantly be draining the PC of video memory that games could make use of, so in actual fact many of your favourite games will probably run faster on Windows XP. Of course after Vista arrives new PCs and hardware will be built especially for Vista which will increase performance anyway.
In the end, that should be clear for everyone. Windows Vista will be heavily bloated and if you don’t plan on disabling all that shiny stuff you will suffer a significant performance loss. I will upgrade to Vista as soon as it’s out, however, I will buy new hardware, too, in fact a complete new custom PC. If my games still don’t run smooth, the shiny stuff gotta go.