A bluetooth standard for navigation (turn left in 500 meters on adams street.) functions would be nice. The only thing I find my car nav does well is put that turn indication next to the speedometer so if I don't hear/understand the directions I can see it at a glance.

Of course my only car with nav is 11 years old, maybe there are other features of more modern systems worth having. I doubt it, but I have to allow for the possibility. The real key here is the car is 11 years old - if you only buy new cars you may fail to realize how bad features such as nav age. When my car was new 3g cell networks were the fast service (4g existed but it was in the early roll out phase), and thus what I would expect my car to have: now 3g is gone - so even if my car had a NAV subscription it couldn't get OTA updates.