Except doesn't it only run on Ubuntu? I looked at it to see if it might be useful for my servers, which are running Debian Wheezy, but the "Other Linux" instructions on the Docker site amount to "install VirtualBox and run Ubuntu" — which, yeah, anything will run anywhere if you just run it in a VM, but that was already true.
Docker is currently easier to run on certain distros than others. But it's not because it's distro-specific. It's because it has kernel requirements which are more easily met on certain distros than others. Those requirements are described at http://docs.docker.io/en/latest/installation/kernel/ (short version: aufs + lxc + (<=2.6 OR >=3.8))
Even just a list of software and kernel deps, then instructions on how to compile the rest of the software by hand would suffice.
For now I've had to muck around reading the Ubuntu packaging files to get a proper idea what/how you install this thing. Which isn't cool. :-(
The hardest part is to provide interchangeable, pluggable storage systems.