Well, neither of us has Nav. Until BMW does something about the idiotic iDrive, I will refuse to get Nav.
Mapquest only helps when you know where you're going. Often, my wife's job requires her to go a client's office on very short notice, and the BMW assist people have actually stayed on the phone with her, talking her through every turn until she gets to her location. Oh yeah, mapquest cannot make hotel or restaurant reservations for you, either.
Yeah, the service is worth the extra five bucks we pay a month, thank you.