The real reason everyone is upset is that I can now say.. goodbye kub, goodbye mesos, goodbye coreos, your are all complicated. I'm thrilled about docker 1.12 and swarm mode.
That's not why. Good for you on using Docker 1.12 with Swarm mode, if that's what works for you. Have fun in production.
I agree. The big guys are scared. I played with it a lot and the new Docker Swarm mode is really, really great. It's the Digital Ocean of orchestration. Granted, 1.12 is the first incarnation, has flaws and is unfit for production, but that will change. I can wait a few months.