I'd been running Ubuntu in a dual boot environment for about 8 months (using the great Wubi to install it) , and finally decided to take the plunge, and go ubuntu as my main OS.
Installing Ubuntu is dead easy, although each time I've done it, i've had to use the alternate cd which is a text based install, not sure why that is.
Being a windows developer, I needed to maintain an environment for development, and I had decided to use VMWare to do this. After seeing the $200 price tag, i decided it was worth a look around for alternatives, enter VirtualBox.
To support the move I got all new hardware as my old AMD 2800XP was showing its age badly, the reason i moved to Ubuntu in the first place.
After a few steps, namely downloading the deb from their site, instead of using the repository, and there are some steps to get usb working on Ubuntu here ( they say they are for 7.04, i did these steps for 7.1 without a problem) It was up and running like a champ!
Installing windows on the virtualBox machine, took about 10 minutes, the fastest by far I have ever seen it install, of course this is thanks to my new hardware, but I was very impressed!
After installing VirtualBox's guest additions into my windows environment (same as the virtual pc, or VMware additions) I can arbitrarily resize my virtualbox, including fullscreen. Which, is pretty amazing, check the video.