For me at least, I made the switch to OS X simply because of software support. There wasn't a good Linux equivalent for Sequel Pro; there's no git gui tool on Linux that matches SourceTree (which my team was standardizing on for its gitflow integration); etc.

And damn, the hardware is just nice. If I could run Fedora on a MacBook Pro, that'd be my ideal setup. Or if OS X wasn't so terrible at customization -- the number of sketchy hacks I've had to install to get my setup how I like it is just depressing.