I can't say I've come across any real negatives so far, but just a caveat that Revolut is not for everyone. You'll likely feel more at home if you've worked in technology and/or startups before, and perhaps also some international experience, especially in locations where the pace is a bit more hectic than the UK.
Other things to note:
* it's fast-paced startup and there's a lot to be done as quickly as possible; I haven't felt pressured to work extra hours, but you do need to be careful not to burn out.
* the company sometimes suffers from a split personality: on the one hand it's finding its feet in the highly regulated world of finance, but it feels more like an innovative fintech focused almost entirely on building an exceptional product; this sometimes involves putting on different hats, depending on what you're doing
* not enough female representation, especially in management (although that's partly to be expected in both finance and technology fields)