The chap showed us the Crossfire system on the latest internal developer build Vista. It managed to run 3Dmark05 flawlessly. We didn't see any issues with it and the Weinand confirmed that a bunch of current games actually work in Vista as well - more than ten titles.
The first shot shows the Crossfire working in Super tiling mode on Vista while the second one shows the AFR, Alternate Frame rendering mode. The performance of the driver is good, and it doesn't feel much slower than what we're used to seeing with Windows XP.
Super Tiling
Alternate Frame rendering