Whether it's worth it or not is a personal choice. What's worth it for one person may not be worth it for another.
It really depends on whether you think it's worth the money. We don't drink alot, except when we're on a cruise. Given that, it still wouldn't pay us to do the drink package. Figure when you're in port 3 to 4 days on a 7-night cruise, most people usually only drink more for a few days.
If you roughly figure $10 a drink, use a high number of drinks and calculate the total amount you might spend if you purchase them separately and compare the total for a drinks package.
It might surprise you, but you really do have to be a fairly heavy drinker to make the packages pay for themself.
Pete