Working with Phoenix, and even more so Elixir and OTP, has been a great joy at a similar to almost the same level I had when transitioning from DotNet to Ruby in 2010 for my experience.
There are still some rough edges, and the job market might be more challenging, but overall I feel anything Elixir related at the moment provides for a high quality filter - both in terms of job opportunities and teams as well as the general product development experience.
I have been pretty happy with Elixir - the syntax takes getting used to, but I'm usually impressed by its elegance.
Phoenix I'm mixed on - it has a few things that "just work" and I'm happy about, but being an opinionated framework I find myself bumping into those opinions the more I want to do things my own way. Usually there's an escape hatch, but being new to both Elixir and Phoenix it's not always obvious to me how to do things when the happy path fails.
There are still some rough edges, and the job market might be more challenging, but overall I feel anything Elixir related at the moment provides for a high quality filter - both in terms of job opportunities and teams as well as the general product development experience.