A friend and I took the Memorial Weekend Cruise out of Tampa with 1 stop in Cozumel. This was my first time using Carnival as my previous 2 cruises were on Royal Caribbean and Norwegian. I have to say after being on all 3, each line offers something the others don't. As far as Carnival goes, I think what I liked the most were the bed linens and the shower and our room steward Melinda who was so attentive and sweet as can be. This is the first ship I have been on with a real shower with a curtain that was square, and not capsule shaped which made navigating around it much better.
I enjoyed the cruise though I think the drinks on the other two lines were better and maybe even colder, but from a price standpoint, completely comparable. The food in the actual dining rooms (I avoid buffets like the plague) was pretty good. There could have been a little more variety each night, but I was pleasantly surprised with the taste/temperature of the food. I do wish the Inspiration had a restaurant that passengers could pay extra to use for dinner, however. We did the your-time dining and enjoyed that, however, we were a bit disappointed that the staff celebration was limited to the dining room that didn't seat the "your time" diners but not a huge loss. the line for your-time dining never took longer than 10 minutes so no complaints there.
My only real criticisms would be that there isn't enough music going on throughout the ship. Carnival is, after all, supposed to be the party ship, but we felt like it was really quiet and needed some perking up with some fun music, such as in the lobby areas and so forth. The calypso band that played by the pool was absolutely fantastic though. The activities were pretty good, except that they are scheduled in such short time frames, that when something really got going, the time expired and it was over (ie the afternoon Karaoke).
We didn't do any Carnival shore excursions in Cozumel but did do the Mr. Sanchos all-inclusive beach club day for $50. Totally worth it, and we felt as though we were hanging out at the beach/pool of a Mexican resort. Not overly fancy but just a fun day out.