My own retrospective... been using OCaml in a production compiler on obscure UNICES since 3.08 (> 15 years!). Pretty seamless, simple updates, everything kept working, lights are still on. I think source changes were required ~3 times, so amazingly stable from my POV :)
It compiles a “C# class”-looking DSL to GNOME GObjects, pushing all the ugly boilerplate (I’m aware there are newer ways to do it that have appeared in the last 15 years :)) into the generated code. And nowadays I’d call it a transpiler, but...
It was written by a teammate in 2004 (Frenchman, obviously!) and I’ve owned it since. A number of people have submitted features, etc. It’s fairly straightforward and OCaml wasn’t really a barrier to entry for any of the contributors.
edit: I should have said “source changes due to OCaml upgrades” above to be more clear.
