We've been running docker in production since late 2013 (data science SaaS). We had some growing pains in the beginning, but since then it has been smooth sailing and a tremendous help in getting our services deployed reliably. However, we have always been very conservative when it comes to upgrading docker and have our own custom glue in place. Still, the statement that "no-one on the planet using Docker seriously AND successfully AND without major hassle" seems majorly hyperbolic.