I've owned numerous gps units in my life, and while the graphics and interoperability of the one in my vehicle are better, it's accuracy is lousy! I personally think that they've not got the gps unit programmed to the proper spheroid and datum as the maps they've supplied, which can register your position quite a bit off. It was better when I was driving it in Europe during the delivery trip around Germany. A good unit should be capable of determining location to around 3-5M on a good day, and 10-20M in bad conditions. Considering BMW is talking about using the gps position eventually to control the transmission shift points and other things, being off that far would mean it would shift at the wrong points...certainly not what they plan.
I sent a note through my sales advisor, but he got promoted and moved to a different location, and I've not heard back...need to bug them when I get back home after the holiday.