Despite my criticisms of FunctionalProgramming, I'm rather getting into this language. (Which is just as well as I've been teaching it this year.)
I think it's got something.
Quora Answer : Considering that learning and understanding Haskell is harder than most of the other languages, what will learning Haskell give you in return, and will it pay off?
Executive Summary :
Yes. If you learn Haskell it will pay off.
Slightly longer and more nuanced answer :
It depends ...
... partly where you're starting from.
If you already know and are using other Functional languages then obviously the value of learning Haskell too is less. If you are a Scala expert then you already know about monads and the way a type-system supports them. Much of the value of FP that's not about types can be picked up from Erlang or Clojure or Elixir too.
... partly whether you are going to use it.
I'm quite a strong believer that you only "learn" a programming language by "doing stuff" with it.
Learning a bit of Haskell by reading a book and just doing a couple of exercises is very different from adopting it to do a project with (even if it's just a personal project)
The value of "learning Haskell" depends on how deeply you engage by how committed you are to using it.
It's possible that, for example, this year, you might learn more about FP from doing a real Python project using FP principles in Python than just reading about Haskell and not using it for anything. Though that's an extreme case.
Bottom line, though. It's worth trying to learn and grok Haskell. Even better is building something with it.