On our last cruise the people in the adjacent cabin spent the first night partying on their balcony to a very late hour - or I guess I should say an early hour. It disrupted our sleep and I was thinking "oh great, 7 more nights of this". But that was the only night they did it, and they were mostly quiet the rest of the cruise.
I am perhaps more sensitive since I spent years at sea in the Navy and knew to respect the quiet of the berthing areas.
Actually the worst neighbors we've ever had weren't all neighbors. I have learned there is a bad side to booking a Carnival cabin too close to the laundromats. On the Carnival Pride in 2002 the laundromat was directly across from our cabin. A family group was aboard and they all descended on the laundry one evening and essentially set up camp. Men had brought chairs from their cabins and were lining the passageway, drinking beer and having a block party while the woman had the laundry door open and were carrying on as they took over the place and were washing, drying, ironing, folding, etc. I half suspected that if I showed up with a bundle of dirty clothes they would have took it and given me a receipt. It was really outrageous. The housekeeping manager and security eventually showed up and broke up the party.