I have found there to be only 2 issues with the navigation in my region:
1) It has some wrong addresses in the POI.
2) It has incorrect speed assumptions for main roads and side roads, versus highway, and consequently uses highway and side roads too much relative to main roads.
I solve option 1 by calling BMW assist every time I need to enter a POI into my navigation and have them send an address to the nav. This works beautifully and is much better than fumbling trying to look for a POI or enter an address into iDrive. In fact with BMW Assist support I love using the nav.
I haven't solved issue 2. Is there anyway to program your speed by type of road on the BMW navigation?
2013 ///M5 Individual Monte Carlo Blue, Platinum Full Individual Merino, Platinum Alcantara, Piano Black, Exec Pkg, Drivers assistance pkg, Bang and Olufsen, 20" wheels, Eisenmann Sport, STIR+, LI Quad HP