The distaste for the OCaml object system is mostly misplaced in the community. While first class modules can mostly replace them — sometimes you really need open recursion. Object types are also a very useful feature used by core libraries.

Ocaml objects are structurally typed which can also be very nice. They definitely have their place.

> and a language that has large features that are almost soft discouraged

It's literally just objects, one large (and early!) feature. Arguably too large compared to the rest of the language: first-class modules or polymorphic variants can handle most of their use cases while being much simpler, and faster than the existing class system. (Objects and object types without the actual classes are maybe ok.)

The only other controversial feature I can think of is Seq and that's just because it can be allocation-heavy. Then again ordinary OCaml lists are not much cheaper (thankfully immutable arrays are already in for 5.4).

Interesting. I'm still working my way through Correct+Efficient+Beautiful. My takeaway so far has been that Modules _are_ the "O" part of OCaml. I guess there's something more "traditionally" an object? Does that mean there were modules in Caml (or whatever the predecessor was) and it was decided classes might be a good feature to add?

Yes, the O in OCaml extends the type system with structurally typed objects and a classic OOP class system.

They're conceptually nice, specially the in-place object syntax, but the class syntax feels tacked on and the overall implementation is very naive compared to a proper OOP runtime like CLR/JVM/JS.

I suggest reaching for them only when first-class modules aren't enough (i.e. you need open recursion). Even then you could sometimes get away with polymorphic variant constraints, but that's admittedly harder to read and understand.