There are a few things like Dockerfile deployments and a `deis pull` workflow for importing your docker images from either DockerHub or an in-house registry as an app, but for the most part you have the right idea. Open-source Heroku has been the general elevator pitch but there are a few docker goodies in there.
> and certain other things like Ceph distributed filesystem
That's an implementation detail of the platform itself, not a hard requirement that you need to set up yourself. We spin up a containerized ceph cluster for database, docker-registry and logger HA.
> if you might want to run a non-Linux node, a specific filesystem or node-local configuration for performance, security or other purposes, or have infrastructure that is not feasibly manageable with a manual process, Deis is not currently useful.
We're quite receptive to suggestions and proposals such as compliance, security, node-local configurations et al. We're always happy to discuss changes in either the mailing list or in an issue in order to make the platform work for a range of environments, so it is definitely possible to bridge these two sides together :)