I'm reasonably happy with the Q7 nav simply because I can search 'online destination' and give the name of the business and most of the time it comes up with the correct address. I also really like the google earth feed. I think it's worth the $15/mo to not have to search in my phone and then plug into the nav, or use my phone and deal with raising/lowering/muting calls/directions/music while also trying to deal with my kid and every other distraction. Hell, if the $15/mo keeps me from having to take my eyes off the road to mess with my phone, it is probably worth it.
2014 Audi Q7
2012 Nissan GT-R
2006 Lamborghini Gallardo Spyder (Audi on the inside)
2003 Lamborghini Murcielago