FYI, if you are tempted to use a virtual machine on top of your Mac OS X, I just switched from VirtualBox (which is free, and convenient) to Parallels Desktop for Mac (not free), and it was well worth it. Parallels is hands down faster, more stable, and a smaller CPU hog than VirtualBox.
I have used VMWare Fusion, previous versions of Parallels, and VIrtualBox on a variety of Apple computers, but this version (Parallels 6.0.11828 I believe) really kicks arses! Then again, free is a cool feature too...
My two cents.