My 65 year old coworker, with an android phone AND gps in his truck, still does this. Well, not the hanging it up from the mirror part, but he goes to Mapquest and prints it out. I've offered to help him figure out his phone or gps several times.
He also has a backup camera on his truck, the kind that comes on automatically obviously (I'm sure they all do), and he never uses it. I've had to yell at him to stop because he's going to hit something he can't see over the back of the bed. A combination of both is the correct way, not only one. But if he were going to choose only one, the camera would be the better choice.