After all the praise at Scale Summit (and from other people I respect) I gave the Docker interactive tutorial a bash.
There were a few subtleties that I hadn't grasped like the way that you can "layer" images in the same way you have git commits on a project. Also the container is linked more intimately to the process it runs than I had imagined.
Looks like virtualisation technologies that might actually be usable by the rest of us. Although only running on Linux 3.8 kernels is a bit of blocker at the moment. I would love this on OSX and allow us to get away from the OSX-Linux disconnect.