I have just got a MacBook Pro and have been using it (+Fusion) to develop on for about a month now. The purpose of this question is similar to Hidden Features of C#; to become a how-to of tips and trick for windows development on a mac.
I should clarify that I am aware of boot camp but do not use it (nor do I have any interest to), hence my use of steady state to make sure nothing happens to my OS partition without my knowledge. However; as Sara pointed out, Apple makes great hardware and I absolutely LOVE the form factor of my MBP so for someone who is looking for a windows only laptop a mac with boot camp should not be overlooked as the hardware is amazing.
My environment is as follows
* MacBook Pro 15" 2.4Ghz 2GB RAM (Going to upgrade to 4GB soon)
* VMWare Fusion 2.0 Beta
* Windows XP Pro SP3 (Slipstreamed BEFORE install)
Tips:
* Use Windows Steady State to keep OS consistent
* Use svn+ssh to connect to the mac for small repositories then use time machine to backup.
* Use spaces.
@Andrew - I'm exactly in your situation. I use a MBP while my company work is purely Microsoft based: i.e., .NET, COM etc. While nothing can beat running Vista natively in Boot Camp (I've never seen Vista run so fast), the niceties of having your Mac OS be the "main" OS, for internet, mail etc. has gotten me to the following configuration. Works like a charm:
For non development occasional need I also keep Microsoft Office 2007 installed. They do have MAC ports, but those don't always cut it.