You know, I always thought this would be the last thing in the world that I'd like to do. But my wife and I did this last year, and it was quite wonderful.
We didn't go that far; just Miami to the Bahamas and out to some island the cruise line owned and Key West and back to Miami. But it's the boat itself that is so lovely.
Sure, the cabins are somewhat cramped (although, that's not a bad thing if you know what I mean; hint, hint). It's the food and the food service that makes it unlike anything else you've ever done. If you like to eat, and I know from some pictures I've seen on some home nodes here, there are folks who fit that category reading this right now, this is something you need to look into.
You will wind up sitting at the same table for every meal, and you will probably meet nice folks you never knew before who will sit there as well. (It sort of reminds you of E2 already, doesn't it?) You will swap your stories and have the best food you've ever had in your life. Breakfast will always be about the same, but lunch and dinner will have a theme which changes each day. There will be American, French, British, Italian, Jamaican, etc. themes. And you can eat as much as you want!
You can order three salads and a side vegetable, or you can order four entrees, or you can get five desserts. It's up to you. The kicker is that the service is absolutely impeccable. The server who is there for you at every meal (ours was a Greek kid) gets to know you like family.
Sure, the sights are great and the boat is fun, but it's the meals that keep folks going on these cruises. Take my word for that.