It really is too bad that the neighbors were allowed to make that much noise. They confiscate so many things from passengers, I am surprised that a boom box causing a noise problem wouldn't be.
Did you call guest relations every night to have security come up, or just the first night?
As NLB noted, in your letter you don't mention notifying guest relations about the shower problem (btw.. every cabin I've been in has a drain in the shower, as well as somewhere in the floor of the bathroom area.)
If you did notify them, they'd have to record it in their logs, and you could have told the cruise lines that was the case, and they could have verified it.
You may not have been happy with the "deck supervior's" response, but I'm not sure who that would have been; a security officer, deck hand?
Again, if you were unhappy about the response it should have been reported to Guest Relations, because they are required to log all complaints.
At least that would made all your complaints verifiable.
As others have pointed out, it's best to report everything, and certainly after the second episode of boom box noise from next door, I would have gone right to the Guest Relations desk, and asked to see the Hotel Director.
He is basically the final authority on all the departments concerned in your complaints.
I have no doubt your complaints were legitimate, however either the hotel manager could have worked to correct them (like changing your cabin), or you'd have had a "paper trail" for the cruise line to follow, which I think would have resulted in at least a discount on future cruise.
Frankly based on your letter, I don't think any cruise line would have handled it differently. They've unfortunately all become quite cynical with people's complaints, just looking for some compensation.
I've talked to many hotel managers about this type of thing; and the stories they tell