One big reason to keep using a dedicated GPS is offline support—as far as I know, both iOS and Android require an internet connection to calculate a route, so if you don't have cell service, you're out of luck. Since dedicated GPS devices have everything locally, they just do all that work without having to talk to a server.
I can't imagine that navigation will work offline. Currently the directions and rerouting are calculated by Google's servers, not on the client device. Obviously trivial routing can be done on the device, but proper routing would need a lot more data to be present, and cover the whole route.
Exactly. Urban navigation, solid, universal navigation, no so much. What is worse is that navigation 'sketchyness' from the likes of signal drop outs. Trying to use my Nexus to navigate from Sacramento CA to San Jose, several complete blackouts along the way, map just goes blank.
And of course its a huge data consumer if its throwing map tiles at you constantly. Clearly local storage is so cheap and geo data changes so slowly that it seems ridiculous that the phone doesn't just keep a cache and save you the net charges but that doesn't seem to be in the plans.
I use the NDrive app for offline mode (pay-per-country-map). Never had a problem with it in several countries, and I go back to Google Navigation when I'm back where data access is. I couldn't imagine using a second GPS unit now after how well the Android is working for me.
I've been using the lab feature, but I was hoping for a bit more.
I would like to be using a web browser on a desktop, perform a search, get directions, and then choose to have the entire route's tiles sent to my phone. (Along with hotel, gas, emergency responder, restaurant place information.)