neil154: I don't have a 9550, so I don't know about the "3G" thing. There must be some notification to show when you don't have full access to the network.
plumcrazy: Yes, it works well if you stay on the beaten path, like main highways, interstates, etc. Once you get outside the cellphone coverage area, you're completely hosed.
I also didn't like that the maps weren't current. Some new roads were created in my area two years ago, the VZ Nav maps were never updated. So, when I detoured onto those roads, VZ Nav would show that I wasn't on a "legal" road.