I use Flow at work, and have plenty of experience with both statically-typed and dynamically-typed languages. I think it's a simple tradeoff- more certainty for

I use Flow at work, and have plenty of experience with both statically-typed and dynamically-typed languages. I think it's a simple tradeoff- more certainty for more toil. It can be a real chore convincing Flow that working code works, and this can force you to use less-readable idioms to make the typechecker happy. It also lards up your code with extra dollar signs, angle brackets, and other crud, making it less readable. These can be acceptable costs depending on your project, particularly the size of it (in lines of code, components, number of engineers, however you care to count).