My only adverse experience is taking me a slightly roundabout route to effectivey turn around - other than that it has been brilliant, taking me door to door even to remote country addresses.
If you put in a post code and house number, you shouldn;t go wrong, but they do require a degree of common sense and a basic sense of where you are going - the famous story of the woman who was going to Stamford Bridge to see Chelsea, and ended up at the original Stamford Bridge is just silly - when you are one hundred miles up the M1 and you should be in Greater London, surely the penny drops?