The Docker image registry and image management should really be a separate program as well - that is a huge pain point that Rocket seems more likely to get right.
I think all in all, CoreOS has built out a ton of tools to make using Docker easier, and they're all very well defined, and compossible. I'd even say that a lot of docker's features could be completely removed by using some of these tools.
Links? Nah just use ips/dns + etcd for service discovery.
Networking? Need very basic bridged networking, and flannel will handle communication on a single host, or multihost.
Deployment? Use fleet.
Not that all these are 100% perfect like I've made them out to be, but any individual component could be swapped out if you want.
I'd like a tool that makes this linking easier outside of Docker, but for now this is one of the features I like about it (although holy moly do Docker links have a lot of baggage you have to bring along for the ride, like giving everything names).
I don't like the sound of locking into one vendor for everything.
I like some of the ideas behind the CoreOS tools, but until they start playing well with others, they're a non-starter for me. I'm not interested in tools that try to lock me into other, inferior, tools.
(I only ask because it doesn't look like it is your core business)