I use GPS a lot, mainly for work but for personal use as well. I look forward to doing field work with my RasPi in hand, connected to my usb gps dongle (about $25), and my (yet to be purchased) 7" rugged screen
For those not familiar with the various range of lower end gps hardware there is a BIG difference in their capabilities.
A gps for vehicle sat/nav ($100-$200. I use a Garmin in my car to cut down on the "stop and ask for directions" prompts coming from the seat beside me). These units typically don't allow you to enter much in the way of custom routes, waypoints or maps. Data updates can be purchased as street and address information get outdated. My data is 3 years old and an update will cost me $100
A basic handheld gps for hiking, biking, etc ($100-$200) has some decent road and off road background mapping, including topographic data, available. Added detail data can sometimes be found available free on the net, or purchased.
A more advanced handheld gps ($300-$500. I use a Garmin GPSmap 76CSx) allows the user to transfer data, including custom tracks and maps to and from their computer. I use mine not only to mark and track where I walked on a property but also to preload my gps with critical property points, lot lines and other custom data from my laptop mapping software (MapInfo) prior to visiting a site.
I do occasionally take my laptop connected to my gps out in the car or into the field but that can be a problem if you aren't careful.
A GPS connected to the RasPi opens up a whole world of capability far beyond anything available from low end gps hardware.