Ask HN: Do you use Docker in production? At scale?

Most of the praise I've heard about Docker thus far has come from developers. But what happens after the images have matured past the development stage and are ready for production?

I'm interested in hearing from Docker users who are putting it into production, both in cloud (virtualized) environments as well as bare metal. What are the benefits? What problems have you run into, and what solutions did you devise? How are you doing day-to-day management and performance analysis?

When answering, if you could tell me the scale at which you've implemented them in production, that would be helpful: it's one thing to run a 10-node service at 10 requests per second; quite another to run a 1,000-node service at 10,000 requests per second.