Example of OCaml's object system in use by the creator of OCaml: https://github.com/xavierleroy/cryptokit/blob/master/src/cry...

OCaml's object and class systems are excellent; I prefer them to just about anything else. They rarely get used for the simple reason that algebraic types, functors, and first-class modules are better suited to modeling almost any kind of domain logic.

Also, I like OCaml's extremely simple and direct syntax. I'm fine with F#'s implicit `in`, though it requires whitespace-sensitivity. I think ReasonML went in the wrong direction, cluttering it up with curly braces and ubiquitous tuple-like syntax for function arguments.

OCaml actually has excellent tooling — among the best — and some (but not many) great libraries. What it lacks most is great documentation...