I don't have evidence just my personal annecdote, but it's such a crutch for me that I sometimes feel embarrased that I can't seem to get around my town of 20 years without punching everything into google maps. What I've started doing is still doing turn-by-turn but putting Google Maps into the fixed North compass mode. It's not quite as convenient but it gives me much more of a sense of direction, kind of like the mini-map in a 3d game.