We set sail on the Mariner of the Seas in October of 2006. My family of four, my wife, 5 year old son and a 13 year old niece stayed in two connecting inside cabins. We were on Deck 7 in the rear part of the ship.
The ship was in great shape. It was very cleaning as the cleaning staff did a great job of keeping the public areas clean. It was a large ship (3100 guests) with many activities going on. I'll cover the activities later on. This ship had the best A/C system out of all the ships I have sailed on. It was always kept cool, both in the public areas as well as in the cabins. There were many lounges and bars where you could sit and enjoy a nice drink. The promenade was great, especially with the 24 hour snack bar and Ben and Jerry's ice cream (extra charge of course). The ship was large, so there was a lot of walking involved. Also the elevators were probably one of the worst I have experienced on any ship. There was always a long wait for one and during the busy times (dinner/shore excursions) good luck on catching one. Even if you do, they were usually full anyway. The up and down buttons also don't always work for some unknown reason.
Let me first describe our cabins. We have sailed on 5 different cruise lines, with this being our first on Royal Caribbean. The designs of the cabins were one of the best that I have been in. There were plenty of storage spaces in the cabin. It also had one of the best designed bathrooms out of all the ships. The semi-circular showers were a genius design, which allowed my wife to take a shower with my 5 year old son. Usually on the other ships, this would have been a very difficult task. The shower also had a hand held feature which was great for giving our little guy a cleaning. The water temperature was hot and pressure was excellent with plenty of towels provided for. The connecting rooms were great with two kids traveling with us. We had all the privacy we needed. My bed however was not very comfortable. The mattress seemed thin and worn. My son's bed however seemed a lot more comfortable. I guess it's a hit or miss.