a friend of mine is going it now and she's on her second assignment...
she does 4 months on a cruise + 2 months off, and I've seen her before/after each phase.
I can say that it really depends on the crew you're working with, it can be real fun as well as hell, but always very hard work.
Keep in mind that cruises are organized with military-style (she has stripes and a title) and that you'll have to follow a looooong list of strict rules, including say "good day how are you doing?" with a huge smile every time you run into a guest, and possibly working below sea level with no window 6 days a week.
I'd say that is not something for everyone, but can be an amazing experience....