In my life before Microsoft, I was a regular VMWare user. When supporting our product, it was always a pain to try to find a machine with a specific configuration (Windows 2000, IE 5.5, .Net 1.1), so we ended up just making a library of virtual machines (we even had some configuration preloaded with Visual Studio and Perforce so you could simply fire up the VM, sync, and start debugging a problem that only occurred in a specific environment). VMWare was simply a fantastic product.
As I was surfing around to catch up on the writings about Windows Live Writer, I stumbled across a post describing a switch to Mac, and a VMWare application that will let you keep using your favorite Windows only products. Wow, does this look awesome.
The cool thing about Fusion though is something called Unity. Unity makes the virtualized applications appear as though they were part of the OSX desktop. Instead of a window showing the Windows desktop and its applications, you get the Windows apps running as part of the regular desktop.