See this article for my initial review of FS One running via Bootcamp on a Macbook Pro.
I have VMWare Fusion 2 and it won't run FS One. Recently I decided to try Parallels 5 to see if it would work. It does! Just about as well as when run under Bootcamp. Frame rate is a little lower, but not enough that I noticed any lag. Graphics all seem to be about the same. I've posted two videos showing the setup. The first has a significantly lower frame rate, but keep in mind I'm recording a huge junk of the screen. The second I'm only recording the frame rate. In both cases, Parallels is running in 'Windowed' mode. 'Full Screen' seems to be a bit faster.
YouTube has an HD version of the first video here.