I think of it as kind of electronic traveller's cheque: really useful but should not be considered indispensable. There's a lot of thought gone into the app, especially the granular security settings, but there should be more to a bank than that.
There's an increasing push here in Germany to go digital but the implementations I've seen are universally shit™, so I'm sticking with paper where I can until some of these people Get a Clue™