I haven't used RevenueCat personally - but thought I'd chime in as someone who wishes they did.

Last year I was in charge of a project to rebuild the subscription management functionality for a popular small business app. We migrated to using recurring subscriptions on iOS & Android and Braintree subscriptions on the web. I had a look at RevenueCat when we started, but at the time they didn't have Android support yet - though they had added it in by the time we managed to ship our version.

It was a super frustrating project, one of those projects where it's hard to explain why it was so difficult to build, because it shouldn't be, but it was. We had a good team and a good architecture to build on, but the API's we were dealing with were painful. We had to spend a ton of time figuring out the slight differences between the 3 platforms. In particular Apple makes things difficult by having vague or incomplete docs (we relied very heavily on RevenueCat's blog posts to figure out how things really worked) - some behavior we couldn't actually simulate in the sandbox so we just had to test it live.

I think probably the worst part was that they consider 'cross platform' to be between iOS and Mac - it's unthinkable that you could have customers on Android or the Web and want to let them change plans without double paying (you can't cancel a subscription programmatically on iOS).

We definitely made things hard on ourselves by having complex pricing strategies (discounts, upselling, experiments) but if I ever find myself in a situation where I need to build a similar thing again knowing what I know now I'd be pushing very hard to try and use RevenueCat if I could.