I got a Garmin nuvi 1390T (with lifetime map updates) for Christmas. I decided to terminate my subscription to VZ Nav.
VZ Nav worked well, but, there is one fatal flaw to the "download maps when needed" concept. Of course, the flaw is that it can only download maps if there is data service available.
I found this out during Thanksgiving vacation. My brothers and I were headed to Jackson Rancheria (an Indian casino in Jackson, CA). It is in the foothills of the Sierra Nevada Mountains and it is just outside the data service area in CA. I was using VZ Nav to navigate to the casino and then intended to use VZ nav to go to a golf course in that area (My brothers and I were going to golf while our parents gambled). Lo and behold, VZ Nav stopped working as we headed to the casino. The data service was very spotty. We had a clear view of the sky, so it wasn't the GPS that was malfunctioning. Luckily, one of my brothers had a laptop with wireless broadband capability. We were able to download map instructions from Google Maps.
I know Garmin Mobile for BlackBerry is available, but decided not to download it since the precious small amount of memory in my 8330 is getting low. My 2-year contract is almost up. I may get a Tour (or Tour2 when it becomes available from Verizon) and load Garmin Mobile on that.
Like I said, VZ Nav works well but I want to be able to navigate even outside the data service area.