I made this happy discovery of using Parallels after being forced for health reasons to switch to only using laptops for my work: I tend to get very caught up in my work and not move for long periods of time while working - this lead to sudden onset deep vein thrombosis and two (nearly fatal) pulmonary embolisms. I am getting better, but my surgeon and doctor strongly suggested that I permanently simply stop working at a desk. It turns out that not using a desk is working well for me: I still use my desk occasionally, but do most of my work using a laptop with a laptop desk stand. An orthopedic chair with ottoman, reclining deck chairs in my yard, couch in our living room, etc. all work well for me, and it is good to move around for variety.
Anyway, now I can still be "in the flow" for long periods of time while working, and I am fine as long as my legs are elevated. I am also careful to take short 15 to 20 minute walks every couple of hours. Before this problem occurred last December, I often hiked in the wilderness behind my house for 8 to 10 hours a week, so I was surprised by the deep vein thrombosis. If you spend a lot of time in a desk chair, please be careful to exercise periodically during the day and not get most of your exercise just one or two days a week - I am writing this hoping to help other people not have the problem that I did.
Parallels: this is a brilliant product for Intel Macs. My wife talked me into buying a nicely loaded MacBook a few weeks ago. I had been happily using a Linux/Windows laptop but now use the MacBook for everything. Windows 2000 and Ubuntu Linux were easy installs on my MacBook, and both "guest" operating systems boot very quickly so if I need to perform a Windows or Linux build, or do some testing, I have fast access to any environment that I need for my work. It is also great being able to share file systems and the system copy/paste buffer. That said, I spend almost all of my time just working in OS X and tend to do quick 10 or 20 minute tasks under Windows or Linux, finish up, and shutdown the guest operating system.