Yes, I wrote a letter after a cruise once, and it resulted in a $400 OBC for our next cruise. We were satisfied with that.
We had purchased 3 bottles of rum in the gift shop. Upon payment, we were told (verbally) the staff would prepare the bottles for our checked luggage back home. Additionally, there was signage on the counter that said all liquor purchases are guaranteed to be packed and prepared for checked luggage. Yep, they used the word "guaranteed". Thirdly, the same verbiage on that countertop sign was ALSO printed in flyers from the gift shop that we received in our cabin. So, they were really pushing this guarantee.
Upon arrival to our home airport, we could smell rum on the baggage carousel. Yep, the bottles were NOT package securely, and had not only broken, but had leaked all over our luggage (and presumably over others' as well, though we couldn't confirm that).
Several items of clothing were ruined (the rum caused colors to run from fabric to fabric -- who knew?), as was the luggage itself.
My immediate phone call to the cruise line wasn't received well by the cruise line. In fact, the gal answering the phone was rude. I'll spare the details at this point.
My follow-up letter resulted in a phone call from a Director of (???) can't remember, but he told me verbally that we'd be receiving a $400 "Goodwill credit" aboard our next cruise.