I used Phoenix for a small project last September, not much more than a toy but anyway...

Pros: websocket support is good, the developers are friendly and answer questions, the app is faster than what I'm used to with Rails.

Neutral: Elixir looks like Ruby but it's very different. Be prepared to learn everything from scratch. You need also to know a little Erlang and the OTP framework to be able to use some useful library functions. OTP is a world on its own.

Cons: the tooling is very immature, probably like the one for Rails at the time of the 1.x releases. Be prepared to write many things by hand instead of requiring gem_x and automagically get functionality for free. This is going to slow down developement, increase costs and possibly get you outbid from competitors. Nevertheless it could be OK for internal projects used to get familiar with the framework.

We've come a long way since September, so please check again. I am outlining our 1.0 remaining milestones Friday at ElixirConfEU. We should see 1.0 in a few months

The websocket support in Phoenix is amazing. And it's not a huge jump to at least get an app up and running if you are a Ruby developer. Most of the really hard things from elixir/erlang have been tucked away nice and neat.

Interestingly, Elixir was created by one of the Rails Core developers mentioned in the article: Jose Valim.

And its vanilla Erlang counterpart, Chicago Boss: http://chicagoboss.org/

And since we're plugging Elixir/Erlang web frameworks, might as well drop a mention of Sugar (disclaimer: I'm one of its contributors): http://sugar-framework.github.io