Man I just hate hearing about stories like your's. I don't have much to say, other than let us know what BMW does for you. I have to think they will make things right. What if you took it back to another dealer?
Anyway, I did use the navigation system on a new 5er in Germany and was very pleased with it. Once I set it to English Language, it worked like a charm. Although the rest of the IDrive interface features kinda sucked. Give me back the buttons, or make the interface work better. The interface was not "fast". It seemed to have a delay which when using something like a "mouse" is terrible. You do things fast and end up waiting to see if it's on the same topic you are.
Good luck