Few issues:
- Tons of bugs (see next point)
- Bigger error/bug surface, 3 languages compared to 1.
- Poor documentation
- Stopped accepting PRs for 1.0 when they decided 2.0 is the way to go (randomly, 2.0 wasn't nearly ready)
- Closing issues without any response (bot that closes them, wtf?)
Check Twitter, Google or whatever and people will mostly say positive stuff about it how they are excited and how fun it is for their TODO List app. We tried building something more sophisticated and it's insane how many things don't work as documented.
Note: react-navigation is also pretty bad, it improved in last year, but there is nothing better in the react-native ecosystem (there used to be something but during my months of inactivity it was removed from the RN itself).
Can probably compile a list of high profile libraries that suck if anyone is interested...