My Magellan is so old it has no map and no PC interface. I fat finger cache positions in using the rocker switch to select the numbers. The need for geocaching is to show your position and the cache position in relation, so something as simple as a Garmin Geko would work. A track back type of feature (shows your breadcrumbs) is nice if you go off trail to find the cache.

GPS is just like the rest of the gear. The basics are often sufficient unto the task, but bells and whistles are oh so pretty...

Tangent: I recently went to look at a new vehicle. The salesman spent more time going through the interactive entertainment features than anything else. I had to ask him to pop the hood so I could see something truly useful.