We came right at lunchtime and had to wait. They issue numbers on paper like at a deli counter, and they call them out only in Italian. The restaurant has lunch-counter ambience but the food is cheap and delicious. It comes quickly and the staff is fun and friendly. I had the Margherita double-cheese and loved it. This was pizza worth looking for in Naples.
The lunchtime line seems to fade quickly. When we had finished, there was no one waiting.
Also, I liked that even though this is a famous place, they haven't capitalized on it or gone tourist.