BMW’s built-in nav system is one of the best I’ve used. It’s not very useful for finding places, but once you have an address entered, the interface to navigate you is superb. Today BMW announced the nav system in some 2007 US vehicles will dynamically reroute you based on live traffic data. No other built-in nav system does this. Even the Acura system will only route around traffic at the start of your trip, any new traffic updates will not change your route mid-trip.
Too bad my 06 can’t be upgraded.