trevelyan makes some good points. I love my MBP, but consider it more of a host machine than a development machine. I do most of my development in VMs or while logged into various Linux machines. If you've never used OS X before, there are a few gotchas that can make it less suitable for cross platform development. Aside from Apple's unpredictable changes to upstream sources, my biggest complaint is the tendency of the Finder to leave turds everywhere it's been. I'm always disappointed when a vendor distributes source code with these intact (and by default, the Finder will try to write them to practically every network drive folder it visits). That's just one example of things you'll have to watch out for when you develop on the Mac.
