Well, I'm just speaking from experience here, but as 'the computer guy' for all my friends and family (as well as for my job), those who have moved to Mac's need my assistance far less than those on PC's. My mom is a perfect case study. She has a small business that for years had 3-4 pc's, each of which inevitably needed some kind of major software maintenance every 18 months to 2 years. Then she started switching to Apple. Her first was a 12" Powerbook. She just retired that machine late last year after 6 years of daily use. I never did a single thing to that computer. And she sold it for $400 after all that time! Same deal with her iMac that is now 5 years old; I've never had to touch it. It's been a similar story with my other friends and family. Whatever the technical reasons or the 'possibility' of getting infected, in the real world, in my experience, they just require far less maintenance.
that sounds legitimate, but you also have to keep in mind the intel switch, which might have changed things. since then, many have agreed that the build quality and resale value have dropped a bit compared to the ppc days
my own macbook i bought in late 2008 for $1500. right now it is worth $850 15 months later. i shudder to think how much it'll be worth in a couple years