With the right app a cellphone/tablet is nearly every bit as good as a dedicated GPS. In some cases better, such as having the ability to use GPS sats, cell towers, and wifi locations in order to get a fix on your location. By "right app" I mean one with not only offline maps but the ability to operate completely without cell service (so it can route, reroute, and access points of interests without using any data). Some such apps are literally the same app that runs on a dedicated GPS.
As for me I primarily rely on listening to the turn directions so don't rely on the screen.
All that said I usually have cell signal and find Google Now--or Siri if on an iPhone--indispensable. I simply say "take me to walmart" and I'm instantly directed to the nearest walmart. Or say any locations to get its phone number--a tap away--and directions, also a tap away. Last weekend I had a bulb burn out and asked for the nearest auto parts store. Google Now was able to understand what I said, and direct to me to a NAPA store that was less than half mile down the road (Siri could have done likewise). My phone responds to "OK Google" at any time, which puts it in listening mode, but I can use my smar****ch to do the same thing and it is more reliable. In case you didn't know you can use Siri/Google Now to remind you of something at a specific location. I use that often (e.g, "remind me to switch off batteries when I get home").
Michael