My husband and I just went on the Spirit on Nov 22. We've only been on one other cruise, so I don't have a lot to compare it with, but we were greatly disappointed in several areas. One was how our room smelled of cigarette smoke every day. The people next to us chained smoked (with two toddlers in their room) and our room filled with smoke. We went to the purser several times and although they put a machine in the room to clean the air, it was a temporary measure. We also had to leave our room during that, so twice late at night we were unable to go to bed because we had to wait for the machine to clear the smoke. The pursors desk refused to talk to the neighboring room because they "didn't want to upset a guest" My husband told them that we were also guests and we were very upset, besides having our health compromised.
The food was not nearly as good as it was on the other cruise we went on (monarch of the seas)....but, they did work with my food allergy by having me pick my food out the night before then altering ingredients to make it safe for me.
We were disappointed with Acapulco, and Manzinillo (although we did the resort excursion and that was beautiful and fun). I realize, however, that my disappointment in the ports has nothing to do with the ship or with Carnival. I just expected them to be prettier.
Also, the shows were horrible compared to Monarch of the Seas. The one saving grace on shift was Jordon Addison the piano bar entertainer and the comedian on the last late night show.
We did have a great time, but it was despite the spirit, not due to it.
Hope that helps your decision.