Actor model is one of these things that really seduces me on paper, but my only exposure to it was in my consulting career, and that was to help migrate away from it. The use case seemed particularly adapted (integration of a bunch of remote devices with spotty connection), but it was practically a nightmare to debug... which was a problem since it was buggy.

To be fair, the problem was probably that particular implementation, but I'm wondering if there's any successful rollout of that model at any significant scale out there.