I guess I'm in a niche market then.
One thing that I've not seen discussed is a POI (Point of Interest) database. There are tons of these on the Internet that you can download and then upload to your GPS unit. As a Volunteer firefighter, I developed a POI database of every Fire Department in my state for use by the Fire Marshal's office. They are uploading them to their GPS units in the Investigator's vehicles. In addition, I'm developing a POI database of every fire hydrant in my department's jurisdiction in order to make water-supply location much easier. Then we will purchase a GPS unit for each fire apparatus and use the database regularly.
Just a couple weeks ago, we used GPS units in a very rural area with heavy tree cover to assist in finding a mentally handicapped person who had wandered away from home. With no reliable cell signal, and with dense forest, we would have been lucky to have been able to use a smartphone to track or log our movements. Once we layed out the search area and followed the GPS data, we were able to find him and return him to his family.
Along those same lines, we have landed the local aeromedial helicopter in rural areas using coordinates from our handheld GPS unit.
If you are only using your GPS for turn-by-turn directions, you are only scratching the surface. These units offer so much more. Oh, and did I mention that a GPS unit doesn't require a data plan?