The thing that impresses me with factorio is how smoothly the game challenges scale with you learning and mastering one game aspect after the other. Basically, you learn something that solves all your current problems, but that directly creates new problems, which you then have to deal with using your newfound powers.

The actor architecture makes it very easy to scale the simulation across several machines and indeed run a simulation cluster that you connect to from a simple client. In fact it already almost works like that. And the only thing that's missing for multiplayer is some UI-level coordination for collaborative planning (basically preventing editing conflicts). Everything else is already "multiplayer ready".