A Powerbook G4. So far it is fucking fantastic. I love OS X. And the quality of the stereo speakers omggggggg
I took the network cable from one of my Windows machines, turned the laptop off, then plugged the cable into the Powerbook. Then I remembered that I needed to transfer some passwords and bookmarks to the Powerbook... so I turned the Windows laptop back on. First thing I see... "Windows has recovered from a serious error".
I've been using Windows XP for years, and I thought it was good - it's only been a few days with OS X, but already I can see myself sticking to Mac in the future. If you haven't ever used a Mac, you should at least check it out. Shit is a little expensive, but not too bad. There is a few things to learn but if you're used to Windows, you should pick them up within a few hours. Safari > Internet Explorer. And Mail > Outlook.
One question for OS X users... how do I minimize all open windows? Windows XP has a "show desktop" button, but I can't find anything like it in OS X.