[tsuyoshi]

When I converted a CPU-intensive program from OCaml to MLton-compiled SML, without changing any of the algorithms, I got a 30% speedup. That was more than 10 years ago though, and both compilers have seen some improvement since.

[c-cube]

OCaml now has flambda, which is a significant improvement on its baseline optimizer. I think the difference wouldn't be that wide today :)