I originally switched from Windows Vista 64bit to Windows 7 Release Candidate (Build 7100) and decided to definitely switch to Win 7. Vista ran fine for me (had SP2 installed), but Win 7 has seemed a little snappier to me. Even with the Release Candidate, I don't think I ever had Windows crash or hang on me.
Windows 7 really, is Vista as it should have been. If you like Vista, you'll love Windows 7. It's the mature, more refined Vista basically.
What you'll have to determine however, if whether you want Ultimate again. I opted for Win 7 Home Premium, as I really had no need for the extra features in Professional/Ultimate versions.
I've also read/seen that Win 7 technically need/uses slightly less resources than Vista as well. So in theory it 'should' perform better on most systems.