In Discord a day or two ago, someone asked if ReasonML is ready for use in business (at least that was the gist of it). I replied that it was ready enough for Facebook to write much of messenger in it.
I see there’s a list of companies using ReasonML at https://reasonml.github.io/en/users-of-reason, but it doesn’t give details of what they’re using it for.
A page giving details, or ReasonML success stories, might be nice.
[edited after looking at linked page]
My company is using it for an upcoming product. I’ll add it to the list when the product gets released. Look for something come Q1 2019.
I’m on that list, third row first column 
I deployed ReasonML to production late last year. I rewrote our technology that allows users to copy content from Microsoft Word and paste into our browser-based editors with better quality HTML than word puts on the clipboard:
https://store.ephox.com/products/powerpaste/
it involved HTML and CSS parsing, along with heavy data manipulation logic of the resulting data model.