Hey Y'all!
Just returned from a great trip to Naples/Sorrento/Amalfi Coast. I've purchased the Campania Artecard (3 days with transit) in the past, it was a good value, and saved the hassle of buying admission, bus, and train tickets. This time, not so much. We purchased it on arrival at the Naples train station TI and used it for the museum and Circumvesuviana to Sorrento. The next day, we were in line (first, to get the good seats!) to hop on the SITA bus, when the driver told is they don't accept the card! We spoke with his colleagues (as everyone else in line filed past us onto the bus, argh!), who told us the rules had changed "last night, where did you buy this?". We ended up having to purchase tickets and nearly missed the bus, irksome, but the rules changing "last night" provided a good running joke for the rest of the trip... Hope this helps!