My wife and I purchased Cheers for the first time on our 8 day Horizon sailing this past March. In the past we paid as we went, and came out "saving money". However, that didn't take into account water bottles, wine bottles, and any other non-alcoholic beverages.
On this trip, we had a total of 45 drinks each, plus countless bottles of water and an occasional ginger ale. Cheers was well worth it for us. Between no longer purchasing water and wine bottles to go along with our cocktails, and it's a no brainer for us going forward. We also used discounted gift cards and OBC to save money on the package.