I've got a Monzo account, which I'm a big fan of. However, Monzo have definitely had more outages and planned maintenance than the other online banking service I use, which is provided by a different UK bank. I'd consider that a reason not to make the jump.
I've been a user since the beta too, and while they do have less outages than when they used a third party payment platform, they certainly still have more outages than my other UK bank.
Other banks and stuff have outages. Monzo just bothers to tell you about issues.
Also the longest outage I remember was when the third party card processor's server broke and it took them a few days to rebuilt it (which is pretty unnaceptable in this day and age)
Is that after they left beta? I noticed quite a few outages, but that was while they still had the big beta disclaimer on things. I've not had any trouble since.
