they have always used macs - in fact, in the first season it seemed as though anyone that was working for the good guys would use a mac, and all the bad people were using pc's!
ive never studied the whole thing to confirm this myself - and i heard that the question came up in an interview with one of the producers, and they said that it wasnt intentional (or something along those lines)
but your right - lots of G5s - one at Kims desk and one in jacks office along with his 17" powerbook (you can tell whos in charge here)
Kiefer Sutherland's, Jack Bauer character also has a 17" powerbook on his desk. The G5 is right behind his desk with a 23" LCD studio display. It must suck to work at CTU if you're a macoholic(lol). With what happens to his character on the show though, I wouldn't want to be Jack. Poor Kelly! How much bad luck can one man have with his personal life.
Macnutt, All the shows on Movie Central air without commercials (have you been watching Carnivalé btw?). 24 is on Fox. You know, the little network that cancels almost every good show they ever make without giving them a chance, and litters them with more ads and product placements than any of the other networks?