Nearly a year ago I was ready to purchase a new laptop. I am a long time Apple/Mac user and hadn't owned a Mac for almost 10 years, primarily because my company requires us to use a couple of programs that are Windows only.
I knew about Virtual PC, but never used it, but I spoke with a friend who is a Mac consultant and he gave me 2 thumbs up. That was for Virtual PC 6, and it has worked flawlessly. Switching from the PC envirement to Mac is instant. Basically, you are switching from one window to another. Version 6 starts and closes a little slow on my PowerBook G4 1.25ghz with 1 gig of ram.
I have since upgraded to Virtual PC 7. It loads and closes MUCH faster and still works as good, if not better.
To me, it is the ultimate laptop and gives you the best of both worlds. I only use the PC side when I must and everything else is Mac including ALL MS Pro Office products, Mail, iCal, Safari, Quicken, etc...
My PC friends drool at my Ultimate, Multi-Platform, Virus AND Spyware Free, and let's not forget, Beautiful G4. It is truly the BMW of computers!