Ugh. Macintoshes. I know pg came out in their favor a while ago ("All the hackers I know are switching to Macs"...something like that). But, man, to see it in reality. My mother has an older OSX machine. What a piece of work. Even the parts of it that are supposed to be good, like the interface, are just clumsy. The mouse is ungainly, with one big "button", making a laughable full-palm-press-down the most reliable way to click. The scrollbars and window-edges are mysteriously hard to grab. The icons in the taskbar would have seemed childish to me when I was 10. The power of Unix is pretty well hidden. If I'm on my linux machine, you can bet I'm not using KDE. Without the shell, linux might as well be Windows.
Now, if it was OSX vs. Windows 98, sure. But XP (*) is stable and the candy colors are easily removed. The security problems only concern the ignorant. I'm not too impressed by people who will pay a 400-800 dollar premium for the geek equivilent of a status symbol.
(*) I've never used Vista.