I decided to take advantage of Parallels' 50% off upgrade offer to try version 3.0, which now has limited support for accelerated 3d graphics. Just to see what it was capable of, I fired up our old favorite game back at Cenzic, BZFlag. With all of the options turned on, running at 720p on a Mac Mini, I was getting frame rates in the mid 20s. That's pretty impressive, I think, for a relatively whimpy machine running in an emulated environment.
So now there really is almost no reason to consider boot camp on a mac anymore, I think. If you really, really require perfect native performance, then why on earth did you buy a mac in the first place?