Another vote for Mac here. I'm on my second, a 1 year old 12" Powerbook (had a 12" iBook for four years before that). My mom has a 12" iBook and my brother has an eMac. My cousin just got a Mac Mini.
The best reason to go Mac is that the operating system, core applications, and hardware are made by the same company. Because of this, there is a level of interoperability and stability that you don't get with Windows, where there are billions of possible hardware configurations.
For those who say, "You can get twice the computer for $x if you buy/build a PC instead of a Mac, you are disregarding three key points.
First, most people don't need that level of computing power for anything other than games. If you really want to play games, drop $200 on an XBox or Playstation that will not need to be upgraded a year from now to play the newest games.
Second, you're paying a premium for OS X, which is a far more elegant, intuitive, and stable operating system than Windows XP.
Third, you get a greater number of preinstalled applications, and of greater quality, with Mac. You get Garageband (easily a $100+ program to buy the equivalent for Windows), iPhoto, great calendar, mail, and address book programs (with the address book integrated across all applications), a web browser that is much better than Internet Explorer, and a Web publishing program (iWeb). To get all of these, you would need to pay quite a bit on Windows. Also, you are NOT paying for adware/spyware/virus software on a Mac, so don't forget to tack on the $50 plus $50 yearly subscription for virus software updates if you're buying Windows.