Former 9 year linux only user here, recently switched to using OS X (mostly) for development. I live in a terminal, always have, and unless I need something specific to linux that will not work on a VM, apart from the mac fancy button crap, I hardly notice a difference. To each his own I guess and at least he stuck with it for a week. Also while most of OS X is closed source, they do use some open source tools: https://www.apple.com/opensource/ but if you want a 100% open system, obviously OS X is not for you.