Sorry I didn't respond sooner as I didn't realize this thread had popped back up again.
To answer your question - no in fact the navigation on the phone has almost caused me to consider getting rid of it.
We've been taking a few road trips this summer and I generally try to use my phone for navigation. In two cases now it has led me through routes that are out of the way and even last weekend had me doing two or three U-turns in order to get on to a highway when there was a direct route there.
Then a couple of other times the map view of the GPS froze while the audio updates continued. So I would look at the screen assuming my GPS was not working but eventually the audio would chime in and tell me what to do next.
It has caused frustration and delay to the point where my wife told me she's ready to throw my phone out of the window next time I try to use it. Now I can probably try to re-enable AT&T's navigator as I never had an issue with it but when I want to speak my request to Cortana it's still going to load the default navigation so it's almost not worth it.
Not sure what to do now as navigation is a key part of owning my phone. We had to resort to using her iPhone 5c directions that she would read off the screen to find our way. Frustrating to say the least!