Zookeeper is a hog, no one will disagree. But etcd is a very awesome yet very new technology. Even the protocol it implements (which is awesome), raft, is very new as a distributed consensus protocol. I'm not in any remote means throwing cold water on k8s, it is fantastic stuff. I only know that there are very very large production mesos clusters today, and the same can not be said (yet) for k8s. Read those two links I posted in the parent though if you have the time. It will make a ton more sense.

That being said, you k8s is sexy stuff, it just ties you to docker, and I believe soon to be rocket. When I first started evaluating both (around docker 1.2.x), docker was not super viable and was pretty buggy. With 1.6.x and newer, most of my original concerns cease to matter. They are both excellent technologies, use whatever works for your environment.