Michael and Denise Okuda (Star Trek Writers, and Graphic Artists)
George W. Bush
George H.W. Bush
Many FBI, CIA, and NSA Field Agents
I know alot of guys in the music world use them. Robbie Williams has a room in his house in LA full or them. It's home recording studio with about 3 power macs in there and he was using a powerbook him self, it was on a show about his new album.