I just phoned NCL. The guidelines have been revised last year. As of November 2004, the passengers can bring wine on board.
Soft drinks: Yes
Liquors: absolutely NOT
Wine: Yes, provided:
1. the wine is not on the wine list
2. $15 corkage fee
The corkage fee applies whenever the wine is opened, whether in the restaurants or in the cabin.
I think the wine in the room will also have corkage fee, if they found the opened bottle in the room, probably. That says, if you open your wine in the room and didn't finish it, there's a chance the cleaning crew will report it to the front desk and they will charge you the corkage fee.
So, do a research of how much is the wine in the store and plus $15, see if you can get a comparable wine from the list. For example, I'm bringing a botttle of new Beaujolais, it's $10 from the store, plus $15 will be $25, and there's a Beaujolais-villages from Louis Jadot that sells for $26 on NCL. For that, I might just buy the wine from NCL.