I've got a Compaq Desktop (Sempron 3100+ running XP and Debian Linux) and a PowerBook (G4 1.33) at home, and a Dell Linux box (P4 3GHz) as my workstation in the office. Surprisingly, I enjoy using all three nearly the same, but if I had to order them, it'd be:
1 - PowerBook
2 - Home Comp.
3 - School Comp - the locations of all the ports/etc on this thing are silly, so it loses points.
Each OS has it's pro's and cons - OS X, I think, is the best of both worlds - the ease-of-use of a mainstream OS and the power of a Unix-like OS. The PB is the best computer I've ever owned, from a form factor/use/reliability standpoint, but when I need to do some heavy lifting, I usually look towards the other computers. The G4 is considerably slower than the other two. I'm looking forward to the 12" MacBook Pro, whenever that comes out.