Very well said. The motherboard in my dual Athlon Debian unstable box recently croaked, and we decided that it would be a great time to switch to a Power Mac. In addition to the reasons you mentioned (Unix under the hood, many free *nix apps available, the system Just Working), OS X appealed to me because its application-centric taskbarless interface is nearly ideal for my preferred working style and I'd heard many a good thing about Apple's interface design and the keyboard support found throughout the OS and applications conforming to Apple's HIG. Thus far, I'm very pleased. Getting used to a new GUI of course involves a learning curve that I'm still climbing, but I've only had this thing for a week and I feel quite comfortable with it already. As a whole, working with OS X and HIG-conformant applications just feels smooth and elegant. I enjoyed using XFce4 and Enlightenment on my old box, but applications and the desktop environment generally did not mesh together in the same way that many of them do on OS X.

Besides, I compose music and would like to eventually set up a home studio of sorts. The particular audio software I'm interested in is only available for OS X. GarageBand is a great basic package that came free with the computer. For more sophisticated work, I would want something like Digital Performer, which gets excellent reviews and, in my experience (a digital music lab in college) is reasonably easy to use for a powerful application.