Kubernetes on Mesos makes sense to me. When you run Kubernetes on GCE, you have all of Google's infrastructure... but if you run it anywhere else, how do you get scale and HA without Mesos? (Let's be frank: when is anybody going to run 100% of their workloads on GCE). I think Kubernetes on Mesos fills the 90% gap of all Kubernetes apps running outside of Google and maybe even on Google for app portability.
You can try it on either Digital Ocean or GCE.
Why there is no try on AWS?
Also I'd like to know why somebody would use kubernetes/Mesos vs. marathon/Mesos ?