My experience with Docker has mainly been in development environments where developers are on different platforms, OSX/Linux/Windows and were the backends were made up of several systems. One other problems I have used Docker to solve is to let Designers that I work with get easy access to a complex system so they can code the HTML/CSS without having to learn and setup everything. Pushing a new image to them has been as easy as pushing new code.
At the Snowsprint this year I tried to setup a docker swarm with 1001 nodes but had to little experience then and Azure was dead slow, at least the way I used it. Crate.IO managed later this year to finalize the cluster and had 1001 Docker Hosts and Crate containers running in a huge cluster. Really cool to see. Working with Azure is much better today then it was 2015 but still it feels little bit slow compared to alternatives. Today Docker Machine works great with Azure and I use it more or less daily. It is quite nice to have a Docker Host in the cloud that you can reboot with more power when needed and not have to listen to the fan in my MacBook Air all day.
In a month I hope to see you in Seattle, 10 years since I was there last time! AirBnb in West Seattle, this year!