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.