I'm using them because they offer me a unix with a nice ui and more premium software options (sorry guys, I'll take something like pixelmator over something like gimp EVERY DAMN TIME)
And that's exactly why I switched from Linux to OS X many years ago (back then on a PowerMac G3). But the mac platform has taken on such a "consumer" focus (both in hardware and software), and in the meantime Linux has come such a long way, that switching back was a no-brainer.