Be prepared for some pretty stiff rates. I was a little surpriused on my first cruise as to how much the ship's excursions were. I've done some, and I think you really have to price compare for the experience you'll be getting.
When you cruise, if you thinking paying for your cruise, flights and taxes/fees is it, you're very wrong. With excursions, beverages, photos, shopping, alt dining, spa etc etc, your ship board account can add up to hundreds of dollars very quickly. I've learned to allow $500 for my account and then at least I know what to expect.
RCI Sovereign of the Seas 2005
Caribbean Princess 2005
Carnival Paradise 2004