To give you a counter-anecdote, I use macbooks in work. For the last five years, I've had two hardware failures and gray screens maybe once every four months. In addition to that, I have issues maybe once a month where the machine more or less locks up (from the logs it looks like windowserver/loginwindow has crashed and OS X is trying to do spindump to them).

Compare that with the _desktop_ Windows 7 machine. It first crashed intermittently (memory failures), but after I changed the motherboard, it has not crashed at all. But then again, I am not using, for example, the most cutting-edge graphic drivers.

I remember quite some crashes during the Windows XP times, but I've since taken a more conservative approach to hardware and drivers.