The negative aspects of cruise ship jobs are obvious: you're effectively trapped in your workplace for most of your contract, with only occasional visits to shore. This can be challenging, particularly at the end of a tiring shift or 'bad day at work'. If you're unhappy with some aspect of your job, you can't just walk out, so you have to be prepared to commit for the full contract, come what may.
As these cruise jobs are contract work, you won't receive paid vacation or other employment benefits. Despite this, the work is financially attractive enough to make it worthwhile and many people save a large amount in a short period of time. You will have so few overheads that it's possible to save a large amount of your income.
Accommodation is provided. Most crew members share two or four to a cabin, matched by gender, nationality and (usually) nature of work. Meals are provided free of charge, so you'll have no subsistence outlay when it comes to your basic needs. Additionally, good crew facilities are usually provided, such as recreation areas, a bar, a gym and deck area. You can buy at duty free prices in the onboard shops and staff discounts often apply to other purchases.
Cruise companies want to keep their staff happy and satisfied, as this will reflect in the service given to passengers. When not on duty, you'll always be able to visit the ports of call and for most people, this is the major attraction.