GPS receivers are only as good as the maps they're used with. If you're proficient with a map and compass, then you're probably familiar with the various types of topography maps. The U.S. Geological Survey is one source of high-quality maps for all areas in the United States. Regardless of where you plan to backpack, it's important you have accurate and easy-to-read maps.
Your receiver will come loaded with a variety of maps. If the maps you want aren't preloaded onto your GPS, you can probably purchase them in CD-ROM format and load them onto your receiver. Some companies also provide microSD memory cards that are preloaded with maps that can easily be added to your GPS. Finally, the Internet has a wealth of downloadable maps available for receivers.
GPS receivers are bound to become a more intimate part of our lives as more people become comfortable with the technology. Some people first learn to use them through their jobs. More and more workplaces are using GPS to track company vehicles or employees who work outside the office.
Once you become proficient with a GPS receiver, you may find you're interested in adding one to your vehicle. Whether you're using a GPS receiver while hiking or driving, the drawback is the same. GPS receivers are not capable of recognizing obstacles in their paths, so both a road detour or a rushing river will require you to reconsider your route. For this reason, it's unlikely that maps will become obsolete any time soon.