Garmin GS815
I bought a Garmin GS815 last year and love it. It's a tad pricey but it has an easy to read display and the auto Nav Kit gives you the maps and the means to mount and power it in your car.
The big reason why I decided on this unit instead of a dedicated auto nav unit was because it is flexible. I can take it anywhere I go, whether it is hiking, biking, or whatever.
The screen is easy to read and with the maps installed on it, I have found it pretty good at routing me where I need to go.
The only downsides I have found with the GS815 is that finding a destination isn't really something you want to try on the road. Another consideration is that the unit has 115MB of built in RAM - I have found I can store an impressive selection of maps in that, but if you're living in a densely populated area, it would limit your total area.
For added amusement, take one on board a jet next time you have to fly somewhere. Odd seeing current speed indicating 400+ MPH!