It depends upon what they are going to use it for.
Personally, I have the cheapest Garmin they sold at the time (a couple of years ago), the eTrex H (high sensitivity). It was a hundred bucks, and the high sensitivity lets me get a signal inside of my house (or out in the woods in the trees.
About the only thing I use it for is finding waypoints; I mark them on my TOPO software, then download them to the unit. When I'm out in the field, the unit leads me to where the places I want to go are.
It makes a neat addition to map and compass, especially useful when I am too lazy/tired/exhausted to navigate by map and compass alone. Lets me cover more ground that way, in some circumstances.
It will never replace map and compass, but it's a nice adjunct.
Jon