One of the things I was looking most forward to for our recent (last week) cruise was putting my phone in airplane mode and leaving it in the room, so I totally get where you are coming from.
Having said that, I did use the app a bit (more and more as the cruise went on) and I did like it. It listed menus for dinner and I liked that I could filter out the activities to search for what I wanted. Sometimes I find the paper Navigator a bit...overwhelming, I guess, but here I could say I just wanted to see what was going on in a certain category (i.e. adult-only experiences only, character meet & greats only, etc.) and it was laid out very cleanly, so I liked that a lot. I didn't use it very much but the times I did use it, the times were correct. I didn't look through it to see what other features were available but I liked it for the streamlined Navigator and the dinner menus (the only features I actually tried out).