Tom-Tom 1 and Garmin Nuvi series came well recommended by Consumers Reports. My experience with a cheapie I got on Woot and the one built-in to DW's Toyota and the testing I did on a commercial satellite based system is: You are paying fairly large $ for convenience. If the thing isn't easy- read: intuitive- and the maps aren't upgradable and available for where you want to go ie: Europe, Hawaii, Asia, Mexico or Caribbean islands, you are better off with a shoebox full of paper maps. Cheap, reliable, available for anywhere, and not a target for thieves.
Jim Ricks