Sorry, I am late to the game on using docker as i was doing 100% xen for my needs, so i was not aware of the amount of work that went into the custom solution.
I like the docker plugin and use it to see the state of my machines and to start/stop them.
Don't necessarily need to replace the existing tools for Fig, but fig sure does make creating/sharing containers easier.
I use my setup for some development work so its nice to let fig create multiple containers with one config.
EX: you can setup a DB,web,redis container set for dev work in one go. Destroy it and recreate it easily as needed.