F# has embraced the OCaml syntax while at the same time cleaning out many of the warts (+., do end etc.). It also now has good tooling available on all platforms.
Despite being a full time javascript/typescript developer I find F# syntax much more appealing and easy to grok than Reason's js inspired syntax.
[1] http://fable.io
Unfortunately, it also drops my favorite thing about OCaml, which is the module system.
I also like that there are different operators for ints and floats. It makes it very clear when you've accidentally mixed the two.
The different operators are a concise way to tell the type-checker that you're working with floats.
Of course, F# has not always been the favorite lovechild of MS, but the OCaml ecosystem does not seem to be in a particularly stellar state either.
Maybe that's a good thing for Facebook?
From an individual standpoint, there are some unique aspects of OCaml that we like a lot. The properties of BuckleScript for example (tiny output, great js interop, fast simple compilation).
No doubt that the ecosystem could be improved, but that's what we're here for and what we're willing to do.
I'm not entirely sure what you're referring to, but OCaml has been around and used for real work for much longer than F#. I'm not sure it's so clear cut.