Last I heard was that for about 2 years after he came back to Apple, he used an IBM Thinkpad, but not with Windoze. I thought it was a hacked NeXT OS or something. The reasoning was mainly for his other day job, Pixar. I have since heard that he uses a Powerbook G4 of some sort, but not exclusively. Steve loves his portables, I doubt he uses anything but a portable for his day to day usage. I am sure though that he messes around on G5s et al, cause he is the boss, and he has to be ready for the keynotes.