There have been some great threads on cruise critic about this - at one point we were considering a quickie HAL cruise this year but opted against it. My husband and I will drink, so when I run the numbers for us, it makes sense. Coming "free" as part of a promo - no question I'd go for it!
Note there are different packages. One is a card with a value of $50 for any drinks you want. The other is the 15 drinks a day, none more than $7 option - that's the one that everyone in a cabin has to buy.
This thread is my favorite - VERY thorough overview of all things boozy on HAL. Took me a few days reading to get through it, but I think all your questions could be answered in it.
http://boards.cruisecritic.com/showthread.php?t=1999316