The actor model is simply magnificent. Once i encountered the actor model, concurrency just clicked for me. Even writing concurrent programs in a non-actor context became simple and easy. It is that amazing.
Every so often when thinking about a system I find I need a default model to go back to. Like when a system seems to be complex or someone is claiming that it has some new property that makes it exceptional or whatever. It's probably possible to pick a few different models but I find the actor model usually covers it. e.g. "Well when you really look at it, it's just a bunch of actors sending messages to each other's addresses/mailboxes"
Hewitt, Meijer and Szyperski: The Actor Model (everything you wanted to know but are afraid to ask)
https://www.youtube.com/watch?v=7erJ1DV_Tlo