I've only ever owned windows. I've used macs, and I get the feeling they're great once you're used to the interface, but I'm a gamer and I use windows. Yes, I know you can partition the drive to run windows compatible games, but I don't use the PC that much for multimedia, mainly for games and word processing, so it's not worth the HDD space/effort.
Also I dislike Apple as a company: they force you to buy stuff that's compatible with their stuff, and they don't let you use iTunes songs with other MP3 players, they don't want you to use their OS on anything else, etc.