My first DCL cruise was December 2000. I had seen pictures of the ship decorated for Christmas, I had been told by the DCL rep how the service was excellent, the food gourmet, etc. I walked on the ship expecting the same service and atmosphere as I was used to at WDW. I was extremely disappointed. Our dining staff was the worst, the food was institutional and many of the crew and CMs seemed to act like they were really not happy to be there, much less help you out. I had been on at least 10 cruised prior so I did know what cruising was all about. I walked off that ship after 3 nights swearing that I would never sail DCL again. I did write my comments on my card, I don't know if they mattered. I have since done the 14 night Magic cruise, and I would say that the difference was like night and day. I was expecting it to be better, I was sailing with a huge group of friends, and it was better. Food and service for me were vastly improved. Both times I had a cat 11, I was expecting a larger cabin the first time, based on sailing Carnival and having a much larger room in their low category, but having been in one 11, I was surprised that my side entry 11 had more open floor space than the standard 11. I expected the food in Palo to be better than it was (on the Magic, didn't go on the Wonder), I didn't like the tea, either.
I sailed on HAL in 2001, I found the service to be excellent, the lounge staff knew my name and drink after the second visit, our waiter were excellent, as was our stateroom host. I have sailed on RCCL and can't remember anything except the excellent beach at Coco Cay and the fact that the pool was only one flight up from my room, so I got plenty of relaxing sun time.
Each cruise line offers a different experience, and each ship with in the line is also different. So what I might not like, others will love and vice versa.