Garmin, for instance, makes a really fine basic device called the eTrex, a very well-designed unit, with a big, legible screen and buttons that allow one-handed operation. Also included are a weather-resistant case and the usual bells and whistles, such as the ability to store up to 50 waypoints on a single route. The eTrex is very reasonably priced at $119 (www.garmin.com). At the high end, Magellan's Meridian ($500; www.magellangps.com) has a color screen, a huge memory that allows storage of detailed road and city maps, plus the ability to track scores of waypoints on up to 20 routes. It's waterproof and even floats.
My own take is that something like the eTrex is fine. It's no less accurate than more expensive models and picks up GPS satellite signals readily. You simply sacrifice a little storage for maps and waypoints. I'd go into a store and try several models, though, to see what "feels" the best and has an interface that seems most intuitive to you.
However, my broad question is, Does anyone really use these things for backcountry navigation? In all the years I've hiked and climbed, I've rarely so much as hauled out a compass. Maps, trails, guidebooks, local knowledge, and common sense are pretty good navigational aids in themselves. GPS units make a lot of sense for boaters, to mark reefs and crab pots (and I know "treasure-hunting" with them is a growing sport), but I truly wonder if many people in the woods whip them out for anything other than amusement. Just a thought.