Alongside the usual performance tweaks in varying game titles etc. there is said to be several Vista related improvements with these as well, particularly with regard to OpenGL.
Catalyst 7.3 introduces OpenGL CrossFire support for the entire ATI Radeon X1000 product series under Microsoft Vista. Users will see significant performance gains in a number of applications when running in CrossFire mode under Windows Vista.
Catalyst 7.3 includes CrossFire enhancements for Windows Vista that enable the Alternate Frame Rendering (AFR) CrossFire rendering mode by default, enabling performance benefits for all AFR compatible applications immediately (including newly released applications that have not been officially profiled for CrossFire). Future Catalyst releases will add further CrossFire performance gains once new applications have been profiled specifically for CrossFire.