Seriously though you sound like the kind of person who'd prefer a Mac, I haven't used one for any great length of time but I'm told it's the best option if you want something easy to use, stable and secure.
Agreed. OSX is one of the finest operating systems ever made, in my opinion. And Apple hardware is good too. It is super-easy to use - in fact, I had problems when I started with it, because I assumed that some tasks would be much harder to accomplish than they actually were. But then you pop open X11 or a terminal, and you're basically using a Linux machine. If you want to - if not, the you don't ever have to see it. Worth every penny.
BTW, there are plenty of nice IM clients that don't screw you with extras - Trillian is the one I use in Windows, and it supports Yahoo! and AOL. Gaim for Linux, Adium for OSX. No need to install crappy programs like AOL or Ymessenger.
BTW2 - Jenda, I have heard a lot of veteran Linux users complain about Ubuntu. I've never used it myself, so I don't know shit about it. I've heard good things from newbs, and bad things from vets. That's all I was saying there.