I'm certainly with Steadman on the "boundaries" thing. But I'm on the whole more aligned in my thinking with Jim. Sometimes it's uncomfortable to challenge conventional wisdom, but in fact there are various pieces of gear we carry where "you're somewhat screwed if it fails". I've used my cell phone as GPS on two long trips, quite infrequently, but never had any problems, and for the AT (special case ...) the maps on my phone were the only maps I carried. 2000+ miles of hiking that way, absolutely no problem, including some decent stretches early on where snow covered the trail completely.

This year I really used a GPS a lot for the first time and it was fantastic. It always "just worked", including once in bitter freezing rain/snow, near whiteout conditions. The CDT is a somewhat special case, just the opposite of the AT in that navigation challenges abound.

Certainly I know how to use map and compass; the Army pounded this into me, and I've helped teach the navigation course for the Seattle Mountaineers a couple of times recently. They do a great job at teaching some basic skills aimed, it would seem, more at off-trail stuff. Because the specific skills they emphasize are things I virtually never use in the backcountry --- triangulation, accurately shooting and following a bearing over short distances, following a bearing via bushwhacking over somewhat longer distances, that sort of thing. In the real world there's no way I'm going to choose to use those techniques when a GPS is so very much easier, better (heck, the "follow the straight line whatever" technique is one that I won't use period, barring perhaps special cases like orienteering).

I think there's a lot of room for various opinions to all be "right" here. A fellow I saw and hiked with a lot on the CDT this year did the whole trip without a GPS. He certainly did get "misplaced" a time or two along the way, but the guy just has a better overall navigation sense than I do built into him (believe me, he wasn't doing much triangulating or the like either, or at least not that I ever saw). We hiked most of New Mexico together, it was obvious that he just had a better spacial feel for things. My wife is like that too; when in doubt we always go with her intuition. Some people just are less prone to "getting lost" in the first place, I think. Me, I use technical skills plus indeed a GPS whenever it makes sense.

So Steadman is right in that very often there is/are some sort of boundary(s) that one can rely on to eventually get located, but I think that Jim is right insofar as the GPS is a really useful tool that I think overall is talked down too much on the fear that it might fail. I don't think that it makes sense to denigrate it because some folks won't have learned how to use it. In fact, I think that would be an excellent reason for courses such as the navigation course that I've helped to teach to address it in at least some rudimentary way, rather than leave it out of the class entirely. Far better IMO to teach the skills that people are likely to use, such as basic GPS skills, just generally a better emphasis on "staying found", and in those places where you do have decent sight lines, using terrain association to orient and locate based on just a hasty "north is that way" bearing and comparing terrain features on the ground with contour lines on the map.