We have used Google Maps a great deal on our current cross country trip. Generally successful with one notable exception. GM directed us onto a road outside of Yosemite labeled "Old Priest Grade," which apparently has warnings posted (we missed them clearly) prohibiting RV traffic. Our 32' Class C barely made it us grades of more than 8-10% and incredibly tight turns. (Note - see our post on the "Roads" on this forum). When we get back, I intend to contact Google to have them correct this very dangerous oversight.
Jim