I was brought up in a Mac environment because of my art background, so I've always been comfortable working with that platform and continue to like it. I still use an older G-4 primarily running Quark, Illustrator, and Photoshop. Since the release of OS X and Jaguar, it is really nice because it's built on the Unix platform. I can open up a shell and work in an extremely powerful environment.
Like Cobalt, I just love how the open source community has evolved and the direction they are going. I have two machines running Mandrake and Debian were I do the majority of my php work and a lot of Telnetting, but I guess Debian is my favorite flavor of Linux.
Ocbaud, I think you'll really like your Powerbook.