The developer experience is great and Phoenix is just a great framework. The speed in which one can create stuff is mind blowing which is going to be the biggest pull factor into the language imo. My main issue is that Elixir is great for a lot of hard problems but for the easy, common problems it is lacking a lot in libraries and so on. It also has a high learning curve.
Although it is probably just going to get better in time the learning curve will probably not.