I downloaded Safari for Vista, and I have been using it for the past days.
Overall, a decent beta, I think.
However, there are a couple of things I hope Apple will improve upon before the final release:
1. The window borders look abit odd. You can only resize Safari window using the square bottom right corner of the window.
2. The resizing of the window is slow -- noticeably slower than IE or Firefox.
3. The text fonts looks kinda fuzzy.
Again, I think given that it is a beta, it is decent. It is quite promising. If Apple can hammer out a good final version with improvements to the above areas, I will easily switch to Safari as my default browser in Vista.