A story about a guy buying a PowerBook is only going to be interesting if you know a bit about the guy. So here's the prequel to the current story. (The aim is to make my prejudices and preconceptions obvious, not to hide them.)
I have owned a computer since I was in primary school. The pedigree went like this: Commodore VIC 20, Commodore 64, various Commodore Amigas, and finally various Intel-based PCs since a 486DX-40 was high-end. I currently run a couple of Pentium 4s.
If you can call the interactive BASIC interpreters of the early Commodores an operating system, then that's the first operating system I ever used. From there, I moved to AmigaOS, which I think was underrated, but probably because only me and a handful of other people in the world ever owned or used it. My first Intel-based PC ran MS-DOS 6 and Windows 3.1. From the get-go, I sensed that Windows was a crock. I had already seen the MacOS GUI, and in comparison, this was at best a not-very-funny joke. I stuck with Wintel over many years, as, I'm sure, have many others, because it was just the path of least resistance. Mac-lovers hear this: we know Windows sucks. It does hurt our brains to use it. But when you live in a software monoculture that wasn't your fault, sometimes you've just got to suck it up.
In the early 1990s, I discovered Unix. I installed FreeBSD when doing so still involved downloading several dozen floppies over a 14.4K link. I've run FreeBSD (often in parallel with Windows) ever since. I choose FreeBSD when I need things to work. I choose Windows when I have no other choice. I've never run Linux, and I've used it about twice. I used Solaris during my undergraduate years. (I have a degree in pure mathematics and computer science.) It didn't do much for me, but at least it was Unix.
I've used Macs many times. I am reasonably sure I used one of the original Macintosh 128 or 512K models somewhere in the distant past. I still remember being blown away the first time I wrote an essay in Word on a Mac, and printed it out on a LaserWriter. (Alright—I was young, and easily impressed.) I've used many incarnations of MacOS. In my first undergraduate year, we programmed in Java on iMacs. Some of my best friends own Macs.
To summarise, probably the single biggest reason I've never bought a Mac is this: I just didn't get it. The Macintosh seemed from the outside to be a bizarre cult, and I really don't care much for religion. A few months ago, I received an iPod as a gift. I like it. (I think the user interface is neat, but it's not "genius" as I keep hearing it described.) Maybe I'm just starting to get it.