I use the map feature on my phone all the time. When I started out I strictly used a map, as I learned pretty much every route I know blind. Now that I'm pretty familiar with all the routes I know, I use the map on the phone as a quick reference if I can't remember a street, or have a missload, etc. Much quicker then pulling out the map book. Plus it automatically pulls up where I am at that time, through GPS, so if I'm looking for a street two or three streets over, it's convenient.
As for the GPS, no. The routes are way to compacted for that to work out. Maybe if you're on a rural route driving 10 miles between stops I could see it working out for you, but when you're driving for 45 seconds between stops, it is not practical to type in the address each time.
On a side note, what I do see happening in the near future is all trucks being equipped with GPS units. Before you all start screaming unrealistic at me, hear me out.
The trucks and DIAD's already have GPS in them. It would not take much for a unit to be installed either with a screen or speaker that works in sync with EDD that automatically directs you to your next stop. Like everything else UPS does, it would be a failure because of improper implementation...But think, their reports would look awesome with no more trace issues.