To chime in as an American Tom Tom user, I love the Tom Tom Navigator 5 I've used interfaced with a Palm Treo 650. The very useful phone is the screen, speaker, and storage for the tiny bluetooth GPS. Could use it walking around a city as much as avoiding traffic on a 12 lane highway.

Only problem, old Treo 650 can only use one bluetooth device at once. GPS or headset, that's it. The new Cingular Treo 680(p) (and their 750w?) support multiple Bluetooth devices. Finally, that makes the Tom Tom Navigator 5 just about perfect.