What's hilarious is that we use both nixos and docker...
I the configuration.nix of NixOS is a nice, small way to get your dev machines configured and installed with the stuff you like. Just copy it on your new machine and off you go :)
I don't know if I would ever use Nix instead of the more language specific packet managers.
It was a very frustrating experience. A frustration which was led by the fact that i could tell how powerful Nixos was - if only i could grok it.
I love nix, my biggest gripe would be that the Nix language is dynamically typed...
I really don't like docker.