I went on a Carnival cruise (Nassau,Bahamas, St. Thomas and one other place) two years ago (in February of course when it's coldest).
Drinks are not included, and non-alcoholic drinks are almost as expensive as alcoholic ones, but they did offer upfront a "drink card" where you paid $50 one-time and had free non-alcoholic drinks the whole time. I'm sure other cruise lines offer something similar. And even for the people that did not get a drink card, there was always water and several juices available. Food is included and there are several places onboard where you get different kinds of food anytime day or night. It's like a big floating city so there's ALWAYS something to do.
If you do it get a balcony room, it's definitely worth it. Waking up to the sight and sound of the ocean right next to your bed is the greatest part of the vacation and what I miss the most.
I spent quite a bit of time in the casino -- I enjoy texas hold'em poker and they had a table for it. I'm _decent_ at it, not pro but can hold my own in home games, and I have to say the poker on the cruise ship was filled with suckers. LOL ok not really, but it's a bunch of people there to have a good time and enjoy vacation, so let's just say while there are some good players there are also people just giving money away.
The total amount I spent the entire time, $900 for the cruise plus the occasional alcoholic beverage, tips for the staff and stewards (which really does make a difference in the level of service you get), a couple port excursions, and miscellaneous, was about $1200. But I came out $600 ahead from the poker (casino closed at 3 am /cry). So I paid for half my trip from the casino and I didn't find the poker game until the 4th day of an 8 day cruise.
I think it's the best vacation I've ever had in my life, I've never been so relaxed and hopeful for the future as I was for that week, and I look forward to going back as soon as I can justify it to myself. It's not the cheapest vacation but the costs are pretty fixed and the pleasure/money ratio is off the chart.
If you're more of an explorer/adventurer with the initiative to direct your own vacation, you might get more out of just picking a place abroad like Europe and visiting it and doing your own thing. But if you want to be pampered and not have to do anything at all if you want, take a cruise. (And there's plenty of stuff to do, on-ship and off-ship if you're bringing along someone who can't stand to stay in one place)