I agree with what RIStrutStopper sez. They are great for that stuff and the fishing use is great too. You can return to the same great fishing spots over and over or tell your buddy the spot precisely.

Another good use is say your out looking over an unfamiliar area. You've been walking all over and now you're lost. It's getting dark. You start finding yourself walking in cirlces. Many guys walk away from where they think they came in. You might think you are miles away from your vehicle, but with a GPS you see that your vehicle is actually nearby.

Most importantly...................ALWAYS carry a few spare sets of batteries.