I have been a Mac person forever. I bought my kids PCs because they are cheap. You get what you pay for.
The latest versions of the Mac OS are the old style mac GUI over a unix core. If you like Unix, (the berserkly variety) you can have that.
I am trying to learn basic programming skills (PHP, MySQL, javascript, Java that sort of thing). The mac has PHP installed, but turned off. If you want to use it, you go into the terminal and make a couple changes to the HTTP conf files and it is on. (PHP 4 on my machine, PHP 5 on the newest versions I understand) It is a breeze to install MySql and run test programs with the two of them. You don't have to do setpaths with Java, the you can just run the programs from your home folder.
Macs are insanely expensive, even used, but they run forever. They are very well engineered. You just don't get as much time talking to the repair guy with macs. Or talking to support. You just don't need to. They can be 30 months or more beyond what is available in windows. Installations are easy, program removals are easy too. I have a game program on my daughter's windows machine that takes up 10 gigs, and Windows can't get rid of it using the uninstall pain. (Any advice on nuking the thing and getting all that hard drive space back would be welcome. )
Safari is way better than explorer (unavailable on the mac now, I think) and Macs are virus resistant. Also the auto upgrade feature is way better. Under vista, upgrades will happen to you when you are working, and suddenly your machine will shut down. The mac system asks permission first. And you choose when to restart. Also Macs require permission to install any program type files.
A whole lot safer, more fun, easier to run, less likely to break. Just better engineering all over the place. But arm and a leg expensive.
You might also look into linux boxes, which have most of the advantages of macs, have tons or really good software, are good for getting into the inner workings of a machine, etc. They are cheaper, less well engineered, but still good value for the money. I don't want to pay for Microsloth office, but there is a really good alternative if you just want to do basic work called open office for free on all berserkly unix installations, including linux.