We have just returned from our first cruise with RCL which we booked because of the wonderful itinerary.From the moment of boarding we could see that there were very big differences compared to the cruises we'd enjoyed with Celebrity:No welcome - No staff member or anyone to welcome us - compared to a drink & smile by Celebrity.We asked one of the entertainment staff to orientate us to where we should go, but they were not very helpful.On entering our stateroom (balcony stateroom) we were not supplied with toiletries other than liquid shampoo in a dispenser & bars of soap. Towels were small & poor quality. Beds were comfortable with lovely sheets & well planned for storage wardrobes.We found the staff excellent, giving us a really good service in all areas of the ship & stateroom of course.We had no hot water several times but inspite of visits from maintence we continued having this problem.The My Time Dining worked very well & throughout the cruise we had excellent service & fairly good vegetarian options. Portions were generous & variety was good.The areas that we noticed the big differences were those of entertainment - there were only two big productions. Both shows were good. Guest performances were by "has beens" or "wanna bees". & many other cruisers felt the same that the shows were poor/average.The last night there was just one performance of a brief & terrible show. We were so disappointed that we had rushed our last evening meal to witness a poor show. We had expected a lot more to end a wonderful holiday but the opposite was the case.The CENTRUM - what a waste of space. There were 3 ariel spectaculars performed here.However, with very little seating available & guests trying to peer from the various balconies on different levels few people were able to see these performances. To add insult to injury during formal evenings the photographs were occupying parts of the area around the Centrum preventing guests right of way causing them to wait & gawk whilst the photographers were taking photos.Several of the Movies that were screened were really not recent - Mama Mia & Skyfall !!!!!On the few sea days, there were no interesting workshops or talks to attend.Overall IMHO I felt that the use of low quality toilet paper, no flowers in public bathrooms, no chocolates on the pillow, no wet towels & cold drinks to greet weary cruisers returning on port days etc etc showed the lack of attention to detail that we so enjoyed on our previous cruise. I am a little reluctant to book RCL in the future although have been told that Oasis Class or other cruise ships are amazing. As we usually chose our cruise because of itinerary, this could be a problem.I like several of the itineries but would not like to sail on Serenade of the Seas again. I would also like to be assured that the entertainment would be much better than it was.