Well, I’ve had the iBook G4 for five months now. I don’t think I could have picked a better laptop. I’ve looked at the 12″ Powerbook G4s, but the only real difference is slightly faster memory and a metal case (versus polycarbonate). I’ve used this every day (taking it back and forth to work) for the past month and a half, and have yet to have a single problem.
Instead of “upgrading” to a Powerbook in a couple of months, I’ll pick up a Mac Mini instead, for the pure “ooh neat its tiny” factor, and replace one of my mini-ITX machines (probably the backup server) with it.