this +100
I (single dev at my startup at that time) adopted Docker 0.4 alpha and i have grown with the docker ecosystem. Today we pay for codeship,etc.
there is zero chance i would have a Docker buy-in if I could not get started then. This is the case with Docker Swarm and k8s today.
I'm struggling with k8s... while the evolution of Docker -> Docker Compose -> Docker Swarm is fairly easy and incremental.
In 2 years time when I have a large devops team... i will spend money on Swarm. Docker Swarm is conquering from the bottom. K8s still has a chance... but it is choosing to compete with OpenStack rather than Docker Compose, which is a big mistake IMHO.