Ask HN: Is it worht learning OCaml?

Yes!

A useful tool for writing OCaml in Vim is Merlin [0].

Facebook uses OCaml as well [1] [2] [3]

A great tutorial is [4]

You might want to learn Standard ML first. The "Programming Languages, Part A" course on Coursera is a good place to start.

Thanks for the tip, how does ML compare to OCaml from an applicability perspective ?

Smaller ecosystem, multiple compilers, simpler language (which can be both good and bad).

Yes, if you want to work for Jane Street Capital.

I am aware Jane Street employs OCaml, is there any other company that is relying on it ?

Here is an obviously incomplete list: http://ocaml.org/learn/companies.html