I enjoyed reading this article today
Its quite complex to begin with and there are quite a few steps involved but I could see power of nix where you dont need dockerfiles but nix can build the docker image itself, its quite useful when you want to distribute apps as docker images, since you can create consistent NixOS base and use same to build and package app, so everything thats used to build the app is then turned into runtime in a docker, so no surprises during deployment.