Our entire infrastructure is built on Elixir. The customer-facing sites, our backend order tracking system, operations, environmental metrics, etc. It's an umbrella app with 3 phoenix front-ends and maybe half a dozen other OTP apps, deployed to EC2 with Distillery.
Doesn't see too much traffic so I can't speak to load handling, but it's really easy to share code (eg, styles across our web front-ends) and the realtime capabilities make for some fun user experiences. Right now whenever we're having a slack conversation or pushing code to github a little heart on our homepage starts beating.