Erlang looks interesting. However, the only problem I have with starting in Erlang is that on the great computer language shootout, it shows that Erlang is about 10x slower than C++ on most examples. And about 3x slower than Go [1] I know that the problems on this website are not specifically "concurrent" problems, but still, even a distributed web-server must do some non-concurrent stuff at times :) Are my concerns…
I still haven't experienced a programming environment that replicates the Erlang/OTP environment. Period.
Haskell is amazing, I've built my company on it, but we're also building our company on Erlang - Haskell's tooling around distributed computing is much more immature than Erlang's (although Haskell's concurrency primitives and STM libraries are extremely mature and arguably better than Erlang's actor model).