c4po
Our dev team seem really happy with this tech stack.
Productivity is awesome - we are four months in and already have similar functionality to a (sort of) competitor that has spent several years on their dev. This is the first dev project I have experienced where we are ahead of our planned milestones. Got to find some more features to quickly add!
My original concern was getting hold of developers as Elixir lacks the pure numbers of people that other server environments enjoy, but this has not been an issue. If anything we have got more senior devs then we would otherwise be able to get as they are excited to be able to use Elixir. Oskar in Poland and Dan in London, hats off, you are awesome!
Not sure if I agree with others that the broader environment is underdeveloped - yes there may be less versions of the same thing compared to a large JavaScript framework, but what is there is absolute quality.
Only (small) gripe is that Elixir is not a fast language. At one stage I thought this was going to be a real issue, but great support from the community and improved understanding on how to do things the Elixir way (let it fail!) seems to have resolved this for us.