Recent episode with a new Garmin GPS (last weekend):

Going to a house in the mountains. Up several winding dirt roads with a bazillion turns required to get to the destination. Nothing new about these dirt roads, they've been there for decades.

Garmin sent us up to a dead end road. It was like an overlook - you climbed a hill and the dead end had views in every direction (over cliffs) except for the road we just drove up. BTW, this overlook was about five miles from the actual destination (as the crow flies, about ten miles as the roads weave).

Then Garmin told us to "turn right". That would have been a death move. So we fired up the cellphones - both an iPhone and an Android phone, and tried to load their respective GPS/maps applications. No go - there was no cell signal up there, let alone a mobile data connection, to download any maps. So while they could tell us our position (Lat/Lon), that was of zero help without a map.

The driver was the one relying on the GPS. Us other two passengers knew better, and we had written down turn my turn directions ahead of time. So after we had proven to our friend that GPS was not really to be trusted in all situations, we promptly found our way to the destination using written instructions and hand-scribbled maps. That was kind of fun, maybe cruel to our friend, but still fun none-the-less. But we made our point.

I think GPS is good for giving you your location, and then you use that with the topo maps you are also carrying. But depending on GPS/online maps alone? Ha! What folly! Even the built in maps on the Garmin were bad.