Soldato
Personally, I think that all the neo-banks are offering something that is slightly unsustainable. I've got Starling (GBP and EUR accounts), Monzo and Revolut. They all have different purposes and are not completely comparable. I like Revolut, as their app has some features you don't get elsewhere. (ie alerts when exchange rate hits a threshold or auto conversion when rates hit a threshold and the ability to top-up in currencies other than GBP.).
Why would Monzo and Starling, that are essentially just retail banks be any more unsustainable than any other highstreet retail bank? They earn their money in the same ways, interest on overdrafts, loans, fees on international transfers, fees on business banking etc..