I'm so glad someone finally said this publically. Everyone always writes posts about how magical docker is, but the reality is that Docker more of a PR engine then a usable production virtualization solution.
People that have used configuration management tools at scale in complex environments have seen that managing state using those respective tools can quickly become tedious. Although the recommendations of the author are fair, its takes a lot of effort to manage state drift on a whole platform using a configuration management tool. But if you use Docker, you will already be forced to think and do things in this new paradigm where there is separation between your data, business logic and service state. You can theoretically achieve the same things with CM tools, but its just harder.
While the whole Docker ecosystem is immature, and people dont know how to deal with things once they get past 1 machine, its getting there and there is slowly more knowledge on how to do service discovery, logging, etc. in large environments. Im sure that in a few years we will look the same way at Docker(and other container tech) like we do at "heavy" virtualization now.
It also is far from mature enough for most. When it fails, good luck finding out whats happening, they don't log stuff. It needs a lot of management around it.
Itll be much more useful when stuff like Flynn takes off, or when someone rewrite this stuff/fix this stuff for average sys admins (and by average im not saying theyre bad, im saying not everyone has an idle army of sysadmins just waiting to fix stuff)