Stateful containers do not move automatically across nodes but we are looking to integrate something like ClusterHQ Flocker (or implement our own using the new Docker plugin api).

For the service discovery part Kontena has builtin dns server. Each service will get their own dns name: <service_name>.kontena.local. And within a service you can point to individual container using <service_name>-<number>.kontena.local. Latest version (0.7) also introduced grid wide etcd so your application can also use that for custom service discovery.

Scaling is handled so that you can easily join new nodes to grid. Services support scaling so you basically just have to define how many service instances you want and Kontena scheduler will deploy instances (containers) across nodes.