I've been following PaaSs built on docker for a while, and it seems like the new swarm mode in version 1.12 makes them pretty much obsolete. I was a huge fan of deis (deis.io), but it seems like they are pivoting away from docker to do something different (deis.com). At this point, think docker has become big enough such that building a platform on top of it is pretty much redundant, but something like this may prove useful for more modular container systems such as rkt.