Why do this? Seriously Mac OS X is only part of the Mac equation (admittedly the biggest part) the other part is Apple's much admired hardware, firstly the build quality is excellent, secondly because they also make the software everything should work properly (after is you control both sides of the hardware/software you really should get it working properly!)

You also won't get iLife, which is another reason people buy Macs...

It seems like a great deal, until you think about it... then it seems that getting a Mac wasn't such a bad deal after all. Don't forget, if you want to run Windows on the system part time that's fully supported on Apple's hardware.