OpenStack Havana is out and includes native Docker support

Very cool. I think actually that will be more useful than just having a docker implementation for Nova as Heat will allow it to be more like a PaaS.

So, I'm not sure either, but I think the AUFS addition makes images easier to sync between machines?

That is, say I start with an Ubuntu image. Then I run an application on it on a Docker cloud. Then I install Python 3.0 and NumPy on it and take a snapshot. And then I want to run the new app with these libraries. I think when you deploy, or when images are being sync'd to machines, they can use the differential compression based on AUFS snapshots. So instead of transferring 300 MB, maybe you will only transfer 30 MB.

That would seem logical based on what I've read. But I have never actually gotten Docker to work, so I don't know. Would appreciate any comments on this.

There is a community that is building Docker images for you. Nova-LXC not so much.

A common container platform that is cross cloud portable for one

Remember, Docker is primarily a container format, not a virtualization platform. Supporting Docker in your own virtualization platform means letting people plug in their pre-made Docker-compatible containers have have them Just Work.