Installed NDrive the other day after my Garmin unit was swiped from my car. (Hidden in glove box, mount out of sight, but they still picked my car for some unknown reason)
I DL'ed the full North America maps on a 7 day free trial, which took 3GB of SD car space & about 6 hours to DL. Luckily, I started in the evening.
I like the NDrive interface for the most part. Some of the yes/no dialog boxes have needlessly small buttons, which is odd, since the buttons for the navigation features & options are nice & large as one would hope.
My first impressions of the navigation were that the routing made good sense in the suburban Tampa Bay area, but the voice instructions did not match the routing well. I'd approach a 90-degree intersection where I was to turn right, and the screen would show this, but the maneuver icon and voice instructions were skipping that maneuver & telling me about the left hand turn coming up after that. And no, they never did tell me about the right turn. There are also places where it tells you to keep right or keep left, and it actually means to TURN right or left.
But be that as it may, I was initially OK with its overall performance. I can get used to certain idiosyncrasies.
What worried me in a serious way was that it suddenly crashed as I drove just past where it was telling me a destination was (it was slightly off, as is to be expected). When I restarted the app, a pop-up asked me if I wished to continue my previous navigation. I chose "no," and nothing happened. Pop-up stayed, no activity. I tried "yes," and nothing happened.
I used Taskiller to close the app, then re-started it. Same result. I re-booted the phone, then re-started NDrive. Same result.
I just finished deleting the app, rebooting the phone, and reinstalling the app. It appears to be functioning now, in that the program is running. I'll be running it constantly throughout the week before I decide if I want to drop $50 on the maps.
Seems difficult to find much info on Navigation apps with offline maps for Android. (I vacation in the mountains out of cell signal range, frequently, need offline maps) Most of the reviews I have found online are for UK & European based apps, most of which aren't available for the North American market. I see that Navigon is working on an Android app, but cannot find an ETA. I'd love to see iNav app, but they don't even have an iCrack app, so I doubt we'll see them on Android any time soon.