I used an iBook G3/G4 12" for several years with linux. I remember the G3 was supported completely out of the box. I loved it: it was small, battery lasted pretty long (I did spend some time fine tuning laptop-mode-tools), suspend-to-ram was working flawlessly and from what I remember all hardware was supported, including 3d graphics (ati radeon). For the G4, I remember there were some issues to get the wireless card working when it came out (Broadcom hardware I think), but the rest of the hardware also worked out of the box.