If I cruise there may be trouble, but if I stay will it be double?

So, you’ve never cruised before, you’ve always toyed with the idea but always thought it might be too expensive, or that you were too young. Your friends finally talk you into it, then you go and watch Titanic again and Leanardo DiCaprio persuades you not too. What should you do?
The following is a short summary of some of the major pros and cons of cruising. I have tried to be as honest as I can, but obviously I’m biased as I love to cruise so feel free to comment and disagree with me or even to add something you feel I’ve missed.