Mac OS X is one of the best OS's you will find out there.
Its simple, its powerful, and it rarely crashes.
I have always like Macs because I always have bad experiences with Windows. At work on Friday, I had to fix 2 W2k machines all day, they drive me insane.
Mac OS 10.2 coming out in the month, has so many features in it, that just makes the best experiences of computing you can have.
http://www.apple.com/macosx/
The Imac is a good consumer solution, it provides all of the solutions and software you can ever need.
Its pro line has much to desired though. There pro line still has SDRAM, which is OK for consumer, but it is not so great for professional users. And they way overpriced for what they are really worth. However, Motorola just announced the G5, and there were leaked sources that Apple's next generation of their pro line will also include DDR RAM.
Macs have most of the software you will ever need. Macs also have the iapps, that are really good for music, movies, burning dvds, photos, syncing, and makes a really good organizer.
Macs does have a lot of games, but it is not a gaming platform. Personally I think I have outgrown games, and really own play them when I have my friends over.
Windows is OK, but I have always felt that its features were a knock-off of other products.