I have watched this show over and over again, and I must say that few shows catch me even a second time. It has a twisted thrillercomedy-feeling that should be intriguing for most, especially David Lynch-fans.
Nick Stahl's interpretation of Ben Hawkins is great, but even greater is Michael J. Anderson's roleplaying as Samson. Anderson is mostly recognised for his role as the wierd dwarf in Twin Peaks, but I must say that his performance in Carnivale is far greater. A third actor worthly to be mentioned is Clancy Brown. He plays a wierd priest named brother Justin, and if Stahl is the hero of this show, Brown is surely the antihero.
However, I think this is one of HBO's finest productions, and thereby one of the greatest ever produced.