I'm in the Denver Metro Area and drive as a Chauffeur.
I'm consistently having problems with the GPS mapping in the mountain town of Evergreen.
Tried it last week and it didn't show my position as accurate, yet my wife's Droid did as she sat in the passenger seat of the same vehicle.
Then, last night, I put in an address to navigate to and it said "follow the directions" but there was a "searching for GPS" at the bottom of the directions and the turn-by-turn didn't work.
It did the same thing when I took my passengers home, then, right after I dropped them off at their home, the turn-by-turn began working again.
I know; Murphy's Law.