How important is Posix?
bayareaguy: I think it only matters for developers who work with mainstream open source.That's me most of the time and my switch from a dual-boot windows/linux configuration to an OSX laptop several years ago has saved me many hours (although I still have to work around odd OSX weirdness here or there but that is pretty easy to work out).  I'm not likely to do Windows-only stuff anytime soon so I don't expect I'll be paying Microsoft anything until their POSIX support is superior to what OSX offers.However if you're not a developer or if you and your customers mainly work with Microsoft-only proprietary stuff then POSIX won't really matter.