I used to to work in a cruise line and beside how nice it looks is actually a very hard work. As many things in life nothing comes free. Yes, you can go to exotic places for "free" but you work everyday (no days off never ever) for around 10 hours or maybe more depending of your department. You work hard for your money and the company but they (your supervisor, manager or someone with authority over you) can just screw you up if you make one simple mistake or simply they don't like you. Cruel and true. The best part in my opinion is that you have the opportunity to work with people all over the world and make friends that likely you wont see any more once you or them left the job on the cruise industry.
Anyway, just check this blog: http://mycruisinglife.com and you will find more information in the good and bad side about the ship life. Personally, in this case I won't be neutral, so I rather let the post to someone else.