Because it's cool, because OsX is the best OS out there.
Well, there might be something you're missing. Something you're badly oversighting. You're moving to the next level of Hell: you're leaving Microsoft (I really don't think you are leaving Linux) for a company which manages to be even more "evil" than Microsoft.
I'm speaking about Apple patching OpenSource inspection tools so they cannot operate on Apple's software. Take dtrace and gdb for instance. They won't work with iTunes. What's more, their patch and protection is easy to bypass, even lame. Why should apple do that? Maybe ISV, maybe patents, we can't know for sure.
I'll let Adadm Leventhal "speak".
Which started me thinking... did they? Surely not. They wouldn't disable DTrace for certain applications.
But that's exactly what Apple's done with their DTrace implementation. The notion of true systemic tracing was a bit too egalitarian for their classist sensibilities
It's all about you. Think where your use of a Mac will take you in a couple of years - remember: web is the next platform - and that's it.