We have older grandkids and the Harmony of the Seas seemed to offer a lot more activities on the ship than others. The shows offered were wonderful.
The complaints were that we were not told on the Blue Hole excursion until we got into our trip that we needed water shoes. It wasn't in the description at all or on the ticket.
The other complaint that I had was that I was allowed to book Sushi making for 10:30 - 11:30 am, and then Guacamole making from 11:30-12:30 pm. We got into the Sushi making class and found out that you didn't allow time for everyone to eat the Sushi. So, you should allow 1 1/2 hr for the Sushi and/or not allow anyone to book directly after an onboard activity.
The cabin was very nice and we had a wonderful Cabin Steward.