Yup, mac are used by both Nits and Gimpy on Undergrads.
In the Fido commercial where that group of people are following around that guy, we see two. One, a clamshell iBook on the table in his bedroom, and he is later using some mac attached to a cinema display.
On of the commercials on Spike TV is just a powerbook sporting a Spike TV sticker in various places, with the last image showing it basically right beside the Apple logo, all in clear view.
On Sex in the City, Carrie uses an old powerbook (wallstreet?).