1. Mac OS X just works.
The Unix foundation of Mac OS X makes it stable, secure, and super fast. There really is no comparison of a PC and a Mac (apples and oranges). I'm not running any ant-virus software to slow me down and I don't need to! It has only crashed once on me but I caused that trying to do some funky things with Fusion. I find myself using it most of the time (75%?) and only resort to my Windows 7 VM for Office applications, VMware stuff, and a few other .Net based apps. Now that Snow Leopard is finally here I'll have even less dependence on Windows with the new Exchange support. But more on that later.....