One major win is that we always maintained our own deployment config format in a centralized repo. That has made it really light weight to build tooling to deploy to either #Mesos or to #Kubernetes during the migration. 

We also have service discovery that spans both clusters, with instances of the same app available from either cluster. We can roll back and forth between Mesos or Kubernetes without any changes to configs. That really lowers the risk of the migration.

There are about 125 services to move. Most of them will be a simple redeploy.