Sinfonia is a beautiful ship. It's so lovely to watch the sea through panoramic windows in the buffet, gym, disco, and on deck. The kind of ship where you always feel connected to the ocean. All the staff we dealt with were friendly and helpful. Shows were very good for what they were (variety, singing, dancing). Not intended to be great stage musicals. Both of the magicians were amazing.
There were sometimes queues for the breakfast restaurant, the beverage stations, and, especially, the ice-cream shop at the pool deck. But we didn't mind at all - the staff were working so hard, and so what if we had to wait 20 minutes for an ice-cream. Especially with those sea-views to gaze at while standing in line! And yes, the deck and buffet area can get dirty sometimes with 2500 people eating all day. But there was not a single minute that we didn't see cleaning staff somewhere on the pool deck, doing their best to keep it clean for us. Cabin was lovely and cleaned twice daily. Only problem was that there was not enough space under the bed for our suitcase (which was medium sized, not at all big).
For those(like me) who like peace and quiet: the pool deck music was never intrusive and besides, I could always find deck space in secluded areas to tan in peace.