We had an open bar and a three course meal. The food was great - especially the guacamole and grilled shrimp. Our server was attentive but not annoying and kept the drinks coming. The ocean was beautiful, the sand soft, and the pool very nice. I don't know how many people were there that day, but we felt like we almost had the place to ourselves.
When we were ready to go a taxi was right there, and got us back to town quickly. The taxi ride is $15 each way, so factor that into your costs. The shopping was good, more selection than Progreso but a little more expensive. We lucked out getting back on board because we were in the shade of the ship.
At Progreso we only needed our S&S cards to get back on the ship, but at Cozumel they asked for ID, so we were glad we had copies of our passports with us (rather than the actual passports which we left in the safe).
Overall, a very good excursion, though a little pricey.
The ruins site was amazing! You could climb on the structures and we got some awesome pictures. It's a pretty large site so be prepared to walk. We were there in early June, and it was very hot and humid - I can't imagine how hot it would be later in the summer. We were most looking forward to swimming in the cenote, but the water level was way down, and the combination of lily pads and little fish that nibbled at my feet was enough to keep me out. I didn't see anyone else swimming in it, either, although I heard other guides talking about it.
We could have stayed longer but decided we'd had enough and ended up doing quite a bit of shopping. Glad we didn't pay the cruise line price for this trip - the local vendors were about $30 cheaper. It turned around to be a good idea to come back early. We watched people getting back on the ship, and saw how long the lines got even 2 hours before sailing. There was no shade and no breeze - no fun.
The discussion boards indicated that a lot of people just go shopping at this port - the prices were good and the vendors will bargain. Now that we've seen a Mayan ruin, I might do the same next time.