I'm a recent convert. I recently added a Mac to my arsenal. I got a 12" iBook G4 directly from Apple.com and I love it!
I was looking for a very small and portable UNIX based laptop (I'm a professional UNIX geek). I looked at Linux, BSD, and Solaris on Intel based laptops. The iBook and OS/X is an awesome combination and I'm completely happy with it. It was only about $1,000 from Apple, then I added memory on my own since I could get it cheaper than Apple was selling it for. I get about 4 hours on a full charge and it's small and light so it's not a pain to take everywhere.
My only issue has been finding a mouse that I like.
I would also recommend the Mac Mini. That's a pretty inexpensive way to get into it and you can use monitor, keyboard, and mouse you probably already have.
Hope this helps.