1. So much faster. I'm getting super consistent 30ms response times on a heavily trafficked web app. AND I did this while completely ripping out a complicated layered caching system that I was using in last iteration of the app. It's just web app talking directly to postgres database, which sounded crazy to me, but actually works.

2. Socket/Channel goodness baked in. I built a real-time chat experience in about a day with Phoenix channels/presence. Makes it quite easy.

3. Less moving parts. Language level support for async tasks and in memory caching lets you do A LOT without installing/managing redis, queues, and other tools. For fancier use cases you still might want to go there, but for a lot of common tasks (send email after user registers for instance) you can go a long way with just Elixir. And you can keep related code together more easily because of this.

4. Easier testing and maintenance. Functional language by nature tends to lead to more modular, maintainable and testable code. Hard to appreciate this until you build a large-ish project with it, but I've found this to be very true.