Elm (type inference) is sort of. While there is a lot of OS type projects used, having bloomberg use it is a plus. Interesting that FB have build system ^Reason^ (build system) doing something similar (OCaml backend->JS) ~ http://facebook.github.io/reason/
Bloomberg and Facebook are two big users of BuckleScript. FB have a couple of folks writing significant stuff in Reason, compiling with BuckleScript, and deploying to user-facing web properties.
I only saw rather simple typing examples, which didn't seem much different from what TypeScript can do.
On the other hand I read often that ocaml doesn't have runtime errors, which I certainly get with TypeScript.
Of course the rest of the book is a great read too if you're so inclined.
It replaces a lot of the idiosyncratic bits of OCaml's syntax with things that feel more appropriate if you're comfortable with other modern languages.
A quick example is tuple types. OCaml declares tuple types as int * int, which makes total sense if you know that tuples are a product type. However, you actually create tuples using commas. Reason throws away the connection to theory and uses the same syntax for types (int, int) and creating values of that type (3, 7).
Happy to answer any questions I didn't get to in the talk as well!
Dart has a large team behind it, an awesome package management infrastructure, a "Dart native" angular 2 library.
I think the tooling isn't available for transforming Reason => JSX in a consistent development environment from what I gather, but I haven't paid attention for a few months.
One reason to define a tool and use language clearly, I interpreted, 'Build Systems Rapidly' as a ^build system^ where in reality Reason is a ^systems language^ to build things quickly.
Some of the tools are fantastic. I would love to have REFMT "dynamically as the window resizes in order to make optimal use of screen real estate while still abiding perfectly by the formatting rules" built into language editors to aid development.