I've found actors (Akka specifically) to be a great model when you have concurrent access to fine grained shared state. It provides such a simple mental model of how to serialize that access. I'm not a fan as a general programming model or even as a general purpose concurrent programming model.
What are your criticisms of actors as a general purpose concurrent programming model?
Vert.x has the "Verticle" abstraction, which more or less corresponds to something like an Actor. It's close enough to where I don't feel like I'm missing much by using it instead of Akka.