I know Jane Street love OCaml, but you have to wonder how much it's cost them in velocity and maintenance. This is a quant firm blogging about a programming language they're the most famous user of.
Jane Street has been one of the most successful financial firms of the last 10 years or so, going from a niche hedge fund to a big player. Sounds like OCaml has been working out for them. Certainly I know it's helped them hire a lot of excellent programmers.