Yesterday I flew a 700NM round trip using RWY on my 5.5" Galaxy S7, for the first time. Being new to this technology I found it was brilliant. It was mounted at dash level to my left, via a suction cap stuck to the windscreen. My co-pilot ran his 10" tablet at the same time, but I was happy just using the smartphone for the whole flight. Everything was legible, zooming in / out was simple, as was changing the map bases underneath the magenta line. I also pulled up NAIPS and Willy Weather mid flight, to check on the latest conditions at our destination - very handy.
I had planned the flight on the phone the day before, so was pretty much ready for the CTA steps, radio changes and conflicts. I carried paper maps too, plus my handwritten flight plan and airstrip mud maps, but could have just as easily jumped to the ERSA diagrams on the phone. I'd say paper maps and flight plans are easier to scan at a glance, but they are often cumbersome and a pain to re-fold while distance flying.
I'm likely to get my own 8" or 10" tablet as a back-up, but was happy with how well the big smartphone did the job. I needed to keep it charged, via cable to the ship supply, and we carried a second battery brick. My phone battery would not have lasted the whole 7 hours - I'm guessing full-time GPS usage chews through the power.