Coincidentally, I chose to look into using OCaml for a project last week. I was pumped and then I was disappointed at the lack of interest in supporting Windows. That just tells me they're not a serious player.
Apart from the too-many-ports problem, I think the main remaining problem is that too many 3rd party libraries require Unix-isms to build, like shell scripts. This necessitates the presence of cygwin for build (but not at runtime). However the ongoing "dune-ification" of the OCaml universe should help fix this since dune can do everything directly from OCaml code. I'm really looking forward to being able to open a powershell window and type "git clone"; "dune build" and have everything just work.