I have a Garmin iQue-3600.
It's basicly a PDA with a built in Satellite antenna and runs the Palm Operating System. Mine came complete with detailed maps of the USA, Canada and Mexico, a car mount with speaker and a docking station for your PC.
I plotted a 1200+ mile trip from Waco, TX to my daughters house about 15 miles north of Zanesville, Ohio. It announced every turn and even guided me around a detour onto dirt roads and always knew exactly where I was. Just as I turned in her driveway the GPS announced "Arriving at destination". Amazing accuracy!
...Rich