I just purchased a MacBook and have the joy of learning a new set of routines and programs, all while reconfiguring my services again. I've used Macs in various work settings but the bulk of my development time has been on Windows, most recently XP.
I will recommend VMWare's Fusion for other Windows users making the switch. Fusion is an $80 program that lets you run Windows through Mac (you have to pay for a fresh version of Windows, a copy of XP put me back $200 at Staples). Apple has an alternative called Boot Camp which lets you install Windows so you can start up in it when you start your computer. This presumably runs faster (there's no Mac OS overhead while in Windows) but Fusion is much more practical since I'm using simultaneously with my Mac programs. The speed is fine, even with lots of Mac programs running. Fusion is also more flexible about disk space allocations.
I'm quite amazed about what it can do. Netflix's Watch Now service is unavailable for Macs but runs fine through my Fusion-powered Windows XP. The Rhapsody music client also works and I'm listening to music as I'm running my Mac programs. In an amazing feat, I was able to use Rhapsody to sync songs on my Palm T/X via USB cable. This is Windows XP running atop Mac OS X syncing digital rights managed-protected data with Palm OS over USB. Really amazing that it all worked!
I'm sticking with Windows XP because of all the nightmare stories I've heard about Vista, but also because it uses less memory and so will run faster. Also, I know XP very well and don't really relish the thought of learning a whole new system in addition to Mac OS. I'm presuming that over time I'll use Windows less and less and will just have it for browser cross-checking purposes and to run the occasional Windows-only software like Rhapsody and Netflix.
Tags: vmwarefusion, mac os, windows xp, windows vista, netflix, rhapsody, boot camp

I'd really like the netflix feature, but I can't bear the thought of dropping $280 to do it.
I would imagine there are places where one could obtain a Windows ISO file without paying...
I wouldn't have paid $180 just for Netflix but for that and Rhapsody (which I use all the time) and for my past programs and for the ability to troubleshoot it's worth it. This latter part is fairly essential, as MS Internet Explorer isn't available for Mac. Since it's the most popular browser and the most prone to display improperly I really do need easy access to a Windows machine for testing.
I guess it's possible that you might be able to use VMWare or Boot Camp to run Linux and then use the WineHQ open source Windows emulator to run MSIE. Whether it can be done and whether it would pass Netflix's ornery DRM protections I can't say.