FWIW, I feel that way about Scala, but not F#.

The only big F# feature I know of that's fallen out of favor is type providers, and, IMO, that's not because the feature was half-baked so much as because it was one of the many casualties of .NET's transition to being a truly cross-platform toolkit.

Because Scala is a truly innovative and experimental language that came out of a programming language research group. That's why there's a lot of features that didn't play out well in real-world. F# started out as .NET rendition of OCaml. Most languages initiated by large crops don't try to be innovative, rather they take approaches introduced by different niche languages (many of them are only for research purpose) and incorporate to their language. Languages that try cater to a large audience should be adopting features from experimental languages.

F#'s relationship has been vastly overblown. The truth is that they're about as closely related as C# and Objective-C. In the same way that the overlap between C# and ObjC is basically just the C bit, the overlap between F# and and OCaml is basically just the ML bit. (Actually, even less than that.) You could say that it was inspired by OCaml, but it includes almost none of what makes OCaml OCaml, and adds a lot of its own new ideas.

To someone who has a passing familiarity with OCaml, but none with F#, can you elaborate? Because I do hear the comparison frequently.

Do people just draw the comparison because they don't actually know of any other ML languages besides OCaml?

I haven't touched OCaml in a while, but the things it has and F# doesn't that I can remember include: Functors (in the ML sense), camlp4, polymorphic variant types, multiple inheritance, class interfaces.

Things F# has that OCaml lacks: Extension methods, units of measure, type providers, quotations, computation expressions, active patterns, overloading.

Probably most of the F# things could be (and perhaps have been) added to OCaml with camlp4, which is more powerful than F#'s quotations. Versus, F# may never be able to have all of OCaml's ad-hoc polymorphism features. So there's that. But I'm mainly meaning to compare what's actually built into the language.

Great point about half-baked features. The investment boils down to risk-reward. Can we say that the features that are introduced into Java at this point are features that have stood the test of time in other languages?

I have already used `records` in some project I work on. To me it does not look too clever / funky. It still looks like very obvious Java code but little more concise.