Just got back from vacation. Dropped the kids off with the grandparents and took a 5 day Caribbean cruise. If you've never done a cruise, I highly recommend it. Start small - 3 - 5 days. I think it's more fun to cruise with a group of friends...
At any rate, it really is good value for money.
Here are my hints for good cruising.
1. If you have any ability to get around on your own, don't bother with the "excursions." I've always been disappointed and found that I could do the same if I made my own arrangements with a lot less waiting around and way less standing in line. E.g. on this last cruise you could get a island bus tour (probaby an old beat up van) for $100/person and it took 6 hours. Instead, our group of 4 rented a car for $55 and visited everywhere we wanted in 4 hours (with 2 of those hours being at a bar on the beach...)
2. Don't pay for the outside cabins, balconies, etc. Buy the cheapest indoor room - you won't spend much time in there anyways, and when the lack of windows is a big benefit if you want to sleep late (it is vacation after all).
3. (this probably varies from line to line - my experience is limited to Royal Caribbean and Carnival so far) the buffet food is the best food on the ship. The dishes are all designed for mass feeding and there are so many choices. The dinner in the main dining room is more hit and miss. And while I've never had a "bad" meal on a cruise, there were some in the main hall that were just "ok." On the other hand, the main dinner is usually a more intimate atmosphere, and some people (like my wife) put a lot of value in that. So we do dinner in the main hall, but go to the buffet for all other meals. (No, not just 3 meals a day, rather 4 - 6 - kinda like hobbits...)