I am sold on TeleNav in the less than a week I've had it. I left for a 79 mile trip from my house into another city. I live in a rural part of Oregon. Where I live the network coverage is very good. However, half way through the trip the coverage goes to NONE for about 35 miles and then comes up strong again. Before I left, I typed in the city name where I wanted to go and TeleNav pulled up the turn-by-turn directions with voice prompts. It worked flawlessly. Even when I got to the 35 mile stretch of road where there was NO coverage, it all still worked just fine. It cached everything and I noticed no hiccups during the trip. It is a GREAT product and I would recommend it to anyone.
I have had no interactions with, or opinions on, Garmin.