If you plan to use an operating system other than Windows within a virtual machine, I'd recommend VMware. (eg Linux, Solaris, BSD, etc.)

For me, it's a VMware setup, as much of my work involves doing nasty things to Linux kernels, and VMware has much better Linux support (unless Parallels has very recently improved in this area).

But if you plan to use Windows in a virtual machine, I have no idea and I'm happy to keep it that way

Having pre-ordered it for half price, I have committed to VMWare Fusion because I have used VMWare in linux and was please with it, so I am a returning customer I guess.

If I need to do something for work I start up Fusion and choose XP and it resumes where I left it last time. I even infected it with a virus to see how good 'snapshot' was. I restore the snapshot once the virus attempted to crash windows and it was like I had never downloaded the file!

Beautiful, I run Avast! & S&D Spybot in Fusion to stop any infections.

I just tried the RC1 of VMWware and found it much better than beta 4 (fewer bugs) but the only thing that annoyed me was not being able to access the task bar - I couldn't get to folders or the control panels quickly. I should note I'm using a very stripped version of XP that runs very fast as a result.

Curra there's a way to enable the toolbar, but you need to hack a parallels tools config file inside windows;

C:\Documents and Settings\All Users\Application Data\VMware\VMware Tools

and then open up tools.conf, then enter in the following line;

unity.showTaskbar = "true"