I’m very happy with zero interest as the cost of running the account.
I think it’s the opportunity cost of the switching incentive that is the question here. In other words, could that money be used in a way to inventivise longer term use of Monzo than by paying joining fees which often encourage carpet bagging.
I previously thought that increasing interest for referrals would be good. Others objected to that on bait and switch grounds - but hopefully Monzo will be collecting some useful data to be able to make an evidence based decision. Or at least some more tests.