Here is a good review of our Garmin 7200. It rests on the dash on a block of wood tied down to keep it from moving around. It tells me how to go to wherever I want either the fastest way or the shortest way, by map and voice, and also tells me when I will arrive. It's FAR better than trying to read a map or a program on a laptop. It will tell me where there is fuel, when is the next Rest Area or campground.
It won't tell me the weather or show radar on the screen and occasionally `forgets' where I am probably due to a hole in the satellite coverage but soon recovers and keeps me on track.
The really bad news is that this model is no longer made but Garmin has many more to choose from.
If you just want to find a city a map will work just fine but if you want to find an address in that city there is no better way than a GPS.