Dune is a great "window" in my experience with OCaml, it forces you to do more than with every other language but you end up with a better understanding of everything.
Kind of disappointed facebook didn't run with ocaml, instead of doing the whole Reason thing. They could have been contributing to and using ocaml directly, instead they decided that programmers will freak out if there's no curly braces.
It's also not on the same planet with tooling pain points.