Perhaps I am drinking too much Toyota Kool Aid, but I like the Nav system.
I had a problem where the thing would route me on slow streets at times when I wished to by-pass an area all together. Once I figured out how to go and change the speeds for given routes, that has gone away.
Maybe the reason I don't mind the system is that I deliberately disabled the voice guidance. I can't stand having people tell me which way to turn and am certainly not going to listen to a woman I don't even know do it. I have a wife to tell me "where to go"!
bigsk8r