Anyone using this in production yet?
CoreOS is still alpha, which is exemplified in this release, which requires a fresh install and isn't upgradeable from the previous release with their auto-update feature.
Also the team is still working out where to put things, filesystems, and how to best integrate etcd, networkd, systemd, etc., with their fleet system for a fully automated, auto-scalable, auto-discovering, self-healing clustering system. All that stuff has come a long way in recent weeks, and I'm very glad to see a distro geared towards both Docker and clustering.
"During our alpha period, Chaos Monkey (i.e. random reboots) is built in and will give you plenty of opportunities to test out systemd." <- https://coreos.com/docs/quickstart/
Our release cadence through the alpha has been about once a week, so 1 "random" reboot a week.
I almost think it's worth it to switch the Chaos Monkey's toggle around: disabled in dev, but enabled in test and prod, to ensure you're using http://12factor.net/ principles in your Docker containers. (I think Heroku does something similar by spontaneously killing containers every once in a while.)