I've been developing on a MBP for maybe 1.5 years now and it is so much better than Windows. I still have no idea how to use the OSX UI really but you can do everything in their close-enough-to-Unix command line. Between that and Homebrew I don't think I'd want to go back to a Windows platform. Only downside is Windows has much more and much freer options for things like XML/XSLT and things of that nature.