My wife and I decided to try Celebrity after many cruises on Royal Caribbean.
Pre-Cruise - there were some frustrations here as we attempted to reach the Butler several times to ask for some amenities prior to boarding but never heard back after 2 messages were left.
Embarkation - excellent, we were in a Sky Suite and really felt taken care of as we were walked to the Suites Lounge but were able to get on the ship immediately.
the Sunset Sky Suite was perfect for our needs. Pictures are attached. Lots of storage space, plenty of room to walk around. Decent sized deck. The bed and pillows were incredibly comfortable. The bathroom was surprisingly large compared to RC but the shower was set really low. I LOVE a rainfall shower head but the problem is, I am 6'4" and my wife, who is 5'8" could only just barely fir under the shower head. So that was unpleasant. Another issue was the toilet paper. Celebrity, if you read this, for the sake of my tuchis, please place something other than the 1 ply sandpaper in the bathrooms!
In Cozumel, they really try to keep you contained in the area right outside the dock. If you want to leave, it is difficult to get out, unless on a tour, and so we stayed right around the dock. I wish we would have arranged transportation so we could have seen more of Cozumel
Lots of shops, but less restaurants than I expected. But Georgetown is a beautiful place. I just wish they had not closed off the beaches, as they said the surf was too rough (which did not seem to be the case from my perspective)