Performance boosts for Lost Planet, Serious Sam 2 and various benchmarks such as 3dMark05 and 06 are seen, and a host of bug fixes for Vista were included. 24 separate fixes for Vista were listed, as well as 11 fixes for Windows XP. Most of them are minor, though some are functionality-related. ATI Overdrive, for instance, is now disabled on certain cards:
The Enable ATI Overdrive clocks for 3d applications is no longer available on non supported products such as the ATI Radeon™ HD 2600 series of product. Further information may be found in topic number 737-28477
If you are using a Radeon, head on over to AMD's site and update.