I have a Garmin Nuvi 755 which I got for $170 off Amazon, but you can get a 255 (which I had before the 755) for a lot cheaper than that (sub-100 a lot of the time).
They're great. I SUCK at directions and my GPS gets me every where. It got me from Kansas City to Ames, IA, and then from KC to Manhattan. It reliably directs me anywhere I want to go through Houston, and has an option to avoid toll roads as well (big bonus in Houston). I've never had it steer me wrong except for one area where it wants me to exit at a spot where there is no exit, but it just recalculates the path (takes about 4 seconds) and we're on the way again. Miss a turn? It just recalculates to tell you either to turn around, or just lays out a new route for you.
Can't speak highly enough about them.