"The locals are cranky and sick of the crowds."
We did experience this, with one waiter in particular, at one of the seafood restaurants on the main street in Vernazza. We sat outside on the deck, which is directly across the street from the restaurant, and the servers are dodging through the pack dropping off and picking up plates. It was getting towards the end of their season and we could see that our waiter was just hanging on, so to speak. He was very honest and pretty much said that by this point merchants and workers are kind of over it. He was nice about it though, and we had a very good, leisurely lunch-the food quality did not suffer-watching all the people flood past.
We could have planned better, but it was fine in the end. I am sure Monterosso handles the crowds better than Vernazza, if we went back, and I think we will one day, we'd stay in Monterosso.