Celebrity offers a similar plan so I did some math. With the plan above you would need to have about 6 or 7 drinks a day to make it pay for itself. If you throw in some fru fru coffees this will pay off for some folks. Not for me.
Remember time you spend on shore drinking will not be covered as well.
A Bad Day At Sea [with power] Always Beats A Good Day At Work
Alaska 2014 - haven't picked a cruise yet
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012
Celebrity: Summit 2011
Princess: Ruby 2010, Caribbean 2013