Elixir's `mix release` is intended to replace (or remove the need for) third-party packages like Distillery. However, it's not there yet, and Distillery is strictly more powerful at the moment.

Notably, Elixir's release implementation does not support hot code upgrades. I use upgrades all the time, and won't be trying out Elixir's releases until this shortcoming is addressed.

What's the benefit of a hot code upgrade vs a blue/green deploy?

speed. A hot code upgrade can deploy a whole cluster in a few seconds. Plus it can keep states safe without rebalancing.

I guess so, I imagine that's up to the maintainer.

The maintainer of Distillery joined the Elixir team to develop releases IIRC.

This is incorrect. I'd feel a lot better if it were true!

Paul went to work for Dockyard with Chris McCord when they started working on this feature for Elixir (and still is).

If he isn't the one writing it, he's certainly been highly involved with the conversation.

I was initially hired at DockYard to work specifically on releases and their eventual integration into core, but I am not a member of the Elixir core team itself :). In any case, that in itself is not really a relevant detail, since José and I talked frequently about the core implementation, so being on the core team wouldn't have changed much there.