I've tried to use flow three times now, but the tooling just isn't there yet. It might be better now, but Facebook doesn't seem to invest heavily in developer UX.
What problem did you have?? I've been using Flow.js for work for several years now, to great success. I feel very uncomfortable now writing plain JS.
Listen, I love pure functional languages, but the step up from JavaScript to flow in program correctness is greater than the step up from flow to elm (in my opinion). Flow even has sum types.
Have you actually tried flow?