Navigation? Really? I don't drive, so maybe I'm somewhat atypical in that sense, but on those rare occasions when I do use my phone to navigate, I find Osmand(+) to be extremely useful.
I drive but I never use navigation as the handful of times I have I've found it distracting and it's led me astray a couple of times. I prefer to just look at a map. Often that nap is on the phone, but I don't need it to tell me where I am or where to go
Navigation for public transit makes a huge difference. Hours every day are saved because of it. And you can "sidetrack" out of your plan thanks to that, while you couldn't do it if you left your bus map at home, or if there were deviations.
