Is there any advantage to buildpacks if you're comfortable making custom Dockerfiles? Seems like Docker would give you a lot more flexibility and clarity over what's deployed.
JSYK: the end result of the Buildpacks project is a Docker image. It's just that if someone wants to package up NGINX inside of a container alongside their app, they can just add the buildpack and an nginx.conf rather than going through the complexity of installing and configuring it themselves.