I like the concept of Docker, but running containers in production has been a bit overwhelming. While they are easy to build, maintenance is a bit tricky.
I tend to use Docker containers for makeshift development environments (especially when I'm forced to work on Windows).
For example, here is my Dockerized version of Laravel Homestead: https://github.com/laraedit/laraedit-docker
It's not the traditional single service per container structure, instead, it is all dependencies rolled into a single container managed by supervisor.
This solution works far better than running a full VM on lower powered devices (like my Surface 3 tablet).
Until I feel more comfortable with CoreOS, I'll probably stick with what I know. But using Docker has drawn me more towards building my applications as a collection of micro services instead of going with the old monolithic approach.