Things I like using it for:
- long running services
- doing anything w/ concurrency
- setting up cron-like processes that run every so often
- actor model anything
- stateful services
- web development using Phoenix & Ecto
- parsing
- encoding/decoding
Things I don't like are primarily related to it being a small enough community. That means libraries for third party services aren't always the best, and using it in the enterprise means that the smaller talent pool is less attractive when the company's priority is to use proven/boring tech for which you can hire tons of developers. I also don't think Elixir has a clear value proposition when you're writing small, single purpose functions for a serverless architecture (even though I really like writing it), or when you're company decides to go all in on Kafka for communication between micro services.
Just my two cents.