We took the Campania Express from Naples to Sorrento, just be aware of the schedule as it is seasonal and only runs a few times a day. We timed it so we would have time in Naples to get some Pizza storing our luggage, about 4 hours. One we purchased our tickets (there was a window to buy tickets at the station) with the passengers gathered in one spot then these two ladies came out in full uniform, little hat and all, and guided us to the tract making sure only ticket holders got on the train. At each stop they would confirm all passengers, and there was a lot, but lot's of people were also turned away. The train itself was nothing special but it was air conditioned and not as packed as the regional train and we had assured seats.