I like Erlang and Elixir quite a bit. However, I do think a bit of caution is warranted. With languages like Java, Ruby or Python, you can probably do an ok job at any particular task. Maybe not a great job, but good enough to get something up and running. I think BEAM has some sweet spots where it really is the best, but they're not huge spaces, and it's good to be wary of people jumping into BEAM without solid reasons why.
In terms of what it's good at, we very successfully employed Erlang as the command and control language for some semi-embedded system medical devices. The runtime is predictable in terms of performance and memory, and fast enough for a lot of things. Where it wasn't, it's easy enough to talk to C. All the fault-tolerant bits are nice for a system like that where you want it to take note of a failure and restart the subsystem that failed. Lots of good logging, introspection and diagnostic tools exist.
In terms of what it's good at, we very successfully employed Erlang as the command and control language for some semi-embedded system medical devices. The runtime is predictable in terms of performance and memory, and fast enough for a lot of things. Where it wasn't, it's easy enough to talk to C. All the fault-tolerant bits are nice for a system like that where you want it to take note of a failure and restart the subsystem that failed. Lots of good logging, introspection and diagnostic tools exist.