Been a Monzo customer from the get-go, as Martin Lewis got my interest on his thoughts on them. For clarity I also have a First Direct account (been with them from the get-go).

Had no issues with Monzo - easy set up, love the app and the instant notifications and easy comms. Get daily spot rate for foreign transactions when travelling & saved us nearly £400 against the tourist rate on our round the world trip). Good benefits available include decent travel insurance and mobile phone insurance. I do not have/use them for business but over the last few years they have been very good.