I get a MacBook because of a class I'm taking. Now I have family members liking the machine, and most likely will be buying iMacs because of the UI, and the fact that they are easier to maintain than their existing Windows boxes. The main thing they like is how relatively quickly an OS X box starts up. Even with the kernel extensions from PGP (I put whole disk encryption on every machine I own) and VMWare, it still goes from zero to being ready to go in less than 60 seconds. Comparatively, my Windows machines which sport at 2-4x the RAM of this MacBook take 3-5 minutes to get from the password prompt of BestCrypt to logged in and usable.
Its not like MacOS has a monopoly on fast startup times. I've seen AIX and Solaris boxes boot about the same. Of course, my RHEL server boots in less than 30 seconds as well. Wonder what it is.
Oh... for a unix weenie like myself, the command:
sudo nvram boot-args="-v"
makes any x86 Mac boot and shut down the way UNIX machines traditionally do.