Let me start by saying I'm the furthest thing from a Mac zealot. I don't own an ipod or an iphone. I bought a powerbook in Jan 2004 because I considered it the best laptop available at the time, and I don't think I was wrong. I've been through quite a few laptops, most fell apart after 24 months. All were plagued with weird windows drivers issues from day one, etc. My powerbook is running strong to this day - a little slow but it runs like a clock. No driver problems, reliable, well built. It's like my '87 mercedes - slow by today's standards, but it's built so well and just works.
On the software side, OS X is a commercial unix that my dad can use, so it's commercially successful. I don't want my parents trying to run Ubuntu or Gentoo because I don't want to be their tech support.