I agree, we have very much approached the problem from that of service administration/management rather than the "build a PaaS"approach. But, I think the "big problem" behind building a heroku style PaaS, is not getting simple scripted deployment to a container -- it is managing relationships between applications, databases, message queues, and other connected services, and I think that is where Juju could be useful to your project.
I'd also be happy to talk more about this any time.
I'd also be happy to talk more about this any time.