The tour operators were great but Viator's arrangements were messed up - had pickup at the wrong hotel - my email instructions fro Viator were poor. Than god the tour operators were flexible and responsible. The tour and trip itself were great. I would use the operators again and highly recommend them, but I would not trust Viator to make the proper arrangements.
Again, tour opererator was great and overcame Viator paper-work deficiencies.