I've read an equal number of horror stories to success for Erlang / Elixir. That isn't to say it's not good or useful, but that it isn't some magic bullet that solves every problem for you.
Edit - I guess my point is that it's not good enough to keep a secret. :)
I've been working in both professionally for several years now and talked with many over that time, at conferences and such, and have yet to hear "horror stories", but such stories could definitely be useful as illustrations on how _not_ to build a system in Erlang or Elixir, so you should share examples!
I _have_ seen some projects with pretty terrible code, but that has nothing to do with Erlang/Elixir, and everything to do with the skill level of the team behind the project.
I've used Java, Erlang, and Elixir professionally and I would never go back to Java. I like being able to write code without the crutch of an IDE. I like not having to deal with JVM deployments. I also like Erlang's functional paradigm and concurrency model a lot better. I'm at least twice as productive in Erlang and Elixir, so I view the two languages as having a competitive advantage over Java.
Edit - I guess my point is that it's not good enough to keep a secret. :)