CM:
I tend to view these GPS the same way I view auto gear boxes, as just another example of de-skilling.
I disagree.
I can read a map, plan my way in, happy days, no problems.
I’d just need to spend a nice few extra minutes sussing out the junction I need, best route in, and go by educated guess on the likely width of a road, where looks likely for a store to be, and how best to approach it. And commit as much to memory as possible to avoid looking at the maps again once moving, or the need to stop and re-affirm key points.
or I can use the GPS, put in the address, look at the map for the area local to the drop on the appropriate view to get the lie of the land, view the low bridge points-of-interest overlay to make sure I’m not going to be stuffed by one of those little lovelies, and off I go. I can concentrate on the hazards that present rhemselves better with a lovely voice telling me in advance where I’ll need to turn, which exit on a roundabout to take (invaluable in brum and london where multiple exits can say the same place but take you to different places) - and if a road is clearly inappropriate for any given reason (traffic, weight limit, width limit, too many parked cars, too tight a turn to be safe or not block things up too badly) then I just carry on and in 2 seconds flat a new route is planned without batting an eyelid instead of needing to stop, check a-to-z and re-plan the approach. more often than not I can see the actual side of the road a drop is on, and how far along and so know which way I need to approach from, where as with maps it’s often a case of arrive, and be wrong so a blind side reverse or drive off to find somewhere to turn round.
so, to sum up it’s not de-skilling at all, it’s complimenting existing skills and allowing more time and effort to be comitted to being safe on ever more demanding roads, than might otherwise be the case.
I agree with auto boxes to an extent though - although with some the prior planning needed to get the wagon on the gas with the time-delay between pedal pressure and power delivery is such that you’ve got to have your wits more about you than in a manual to avoid being stranded waiting for huuuuuge gaps to present themselves in traffic 
the new MANs for example.
