Quite honestly, it's never a problem. In fact, I think it's a huge advantage. I simply would not be willing to give up the ability to change an actor's behavior dynamically.

We use the FSM helper [1] heavily in our backend at Conspire. For data-pipeline use cases, it's invaluable. Keeps our code concise, readable and testable. Even basic become/unbecome operations are big for us, I've written up one of their use cases on our blog [2].

[1] http://doc.akka.io/docs/akka/2.2.3/scala/fsm.html

[2] http://blog.goconspire.com/post/64901258135/akka-at-conspire...