We just returned home from 11 days "on the beautiful Mariner of the Seas." It was an amazing vacation. The ship itself is in great shape. It's not new but you could hardly tell unless you were looking closely. (Hope that isn't how you spend your vacation.) :) There were over 3,000 guests on our cruise but you couldn't tell, with all of the activities available they did a great job of keeping everyone spread out.
The itinerary was excellent, Italy, Turkey, and Greece. We couldn't have asked for a more diverse look at the Mediterranean and its culture. The ports of call were many and the cruise staff was excellent and attentive. Our cabin steward, Dennis was excellent, singing while he cleaned and always making sure we had what we needed without being intrusive.
My only complaint was the food in the Windjammer and the coffee on the ship it was awful. The buffet food was often cold and overcooked. They, in my opinion, spend too much energy making a lot of food instead of a few choices from each nationality and doing them excellent. We ate often in the dining room because the food was much better there but then even lunch took an hour. I gained 5 lbs though so I obviously didn't starve.