OP stated s/he comes from an OOP background, and expanding into FP is a big step into expanding the ways you think about programming, and gives you new tools to solve problems with.
My job is still OOP, but the experience I've gained learning FP has helped me a lot to come up with different solutions I may have never thought up before.
Scala is a fine language, but limited, largely serves as gate way drug to other FP languages. Its a very good starting point.
Haskell is odd and the type system is I feel restrictive. Also the community is really addicted to big mathy words. I do love its notation at the same time :\
F# is pretty much universally loved (from what I gather, I haven't used it myself), and now that the .NET run time is unbolted from windows it might start gaining traction.
oCaml I haven't used so I can't comment.
Erlang is VERY popular, especially with the backend FP crowd since it does concurrency very simply. I haven't used it.
Can you elaborate on this? After using Haskell for some time now I can't seem to come up with use cases where the type system is/would be restrictive.
I've been learning, myself, and really enjoying myself.
It seems to have a pretty solid web ecosystem, can use the best parts of java, and is a lisp with optional mutability for when you feel you need it.
I'm not disappointed I chose it, I can say that much.