Just to clarify.... since we're specifically on the AT forum, we are talking about using a GPS on the AT itself, correct? Judging by the majority of "no" responses, I think this is the case.
One has to try really, really hard to get lost along the AT corridor, though admittedly I did get off the trail accidentally in Connecticut, though it was easy to get back on.
I realize it is fun to record tracks though, and I do so on other trails all the time, and store them in a growing library. Just can't justify burning precious battery power on the AT though.
I have a fairly new model Garmin (30-something) that is now basically useless, because my cell phone keep just as accurate of a track. Might even be better. Basically, I no longer see any need whatsoever for a standalone GPS unit. I suspect they will be obsolete very soon, except for high end units for surveyors, military, etc.