Rick,
I use Mac OS X almost exclusively. Once in a while, if I have to,
I will fire up Windows XP in a VM image. There are some
applications in the PTC tool suite that don't run under OS X,
like ProductView and Arbortext, so I use a VM for that. But
for software development and general high level system architecture
type tasks, which is where I tend to spend most of my time these
days, I can stay in the Mac world.
Ron