Monitors, linking, supervision trees, vm-level introspection into the state of the actors, distribution primitives that make actor identity nonlocal across clus

Monitors, linking, supervision trees, vm-level introspection into the state of the actors, distribution primitives that make actor identity nonlocal across clusters, actor cancellation (like kill -KILL), graceful actor shutdown, sane id serialization (how easy is it for me to serialize an actor Id, put it on a kafka queue and have it come back in a response so I can route the response back to the actor) etc, etc, etc.