This was our second cruise but first cruise on RCCL. (We previously sailed the Golden Princess.) My husband I and were traveling with our parents and siblings --8 total. The embarkation process went smoothly; the line was long, but moved quickly. Once we got on the ship, we had lunch and hung out in Windjammer's, as our entire party was told that our cabins would not be ready for an hour and a half to two hours. Windjammer's was crowded, so I guess most passengers were in the same situation.
The ship itself is beautiful and tastefully decorated. Our cabin was spacious; in fact, it was much larger than our balcony cabin on the Golden Princess. However, service on the ship was impersonal and left something to be desired. For example, the earliest our cabin was serviced was 1:30 in the afternoon; a couple of days, it was after 3 when our cabin was serviced. My mother-in-law has sailed on RCCL 3 times previously (older classes of ships),and she was disappointed in the service, as well. With 3500 passengers aboard, maybe good service was too much to expect.
We had second seating for dinner, which varied from 8:30 to 9:00. We tried to change it to the main seating, but could not. Most nights, it was 9:30 by the time we ate, which was too late. (My father is diabetic and needs to eat at relatively regular intervals.) The first night of the cruise, the wait staff seemed disinterested and service was poor; we decided to eat in Windjammer's the second night. When we returned to the dining room the third night (and from thereafter), we received much more attentive and responsive service. Having sailed on Princess, which has Personal Choice dining, I have to say that my husband and I disliked the regimented eating times on Mariner. In addition, there were large blocks of time when Windjammers and the dining room were closed.