My husband and I sailed 2 years ago for New Year's Eve. It was great fun. It happened to be formal night and at midnight there was a big party on the Lido deck with free champagne and Caribbean music and party favors and of course the big countdown!
We had a conga line the whole way up the deck. It was a blast. We did have a somber moment to remember 9-11 since it was still pretty fresh, but after that everyone let loose, even the bar staff got into the dancing.