Last cruise our chees package had paid for itself by midday on day 4 of 7. We did not change our normal vacation behavior to "maximize ", just got what we wanted, when we wanted. Definitely worth it!
That being said it isn't worth it for everyone. If you don't have multiple alcoholic drinks a day it probably won't work out for you. It really depends on what an how you drink. We enjoy cocktails, drink sodas, and like to have bottled water in our room. Someone who will just have a couple of beers by the pool likely won't get the same value.