Earlier this year I bought a gps unit. I was considering a Garmin, a TomTom, and a Magellan. I read that the Garmin uses a mapping program from the U.S, and the TomTom uses a mapping program from Europe. It was reported that the Garmin would supposedly give more accurate maps of the U.S., while the TomTom would give more accurate maps of Europe. I don't recall what the Magellan uses.
I ended up buying a Garmin 760G. It's got an mp3 player, bluetooth capabilities for cellphones, and an FM transmitter. I know some other people who have TomToms, Motorolas and they're all happy with the ones they chose.