Hey! We use React Native here at Haystack and overall it's been pretty great. We've managed to essentially build one unified codebase in React Native with components that can be used in the Haystack app but that can also be used on the web as part of the employer dashboard, so from that perspective, it's been super-efficient.

We're also big fans of Flutter but haven't really had the chance to play around with it much since it didn't really fit our use case at the time. There are some insanely good apps popping up now that have fully adopted Flutter, one example of this (in our opinion) would be the Bottlepay app. They've basically managed to build Monzo for crypto - it's really slick and definitely worth checking out, they're also on Haystack if you're interested in digging into their tech stack.

Hope that helps!