This was our family's first time on Princess. We've previously sailed on Carnival, Holland America and Celebrity. By far, Princess had the worst food, the worst entertainment and the worst on-board activities of any ship we've ever sailed on.
The Sun Princess's set up with two smallish theatres instead of one large theatre makes it impossible to put on any of the "Broadway style" shows the other lines do. They repeated the same show over and over again so there was little variety. When they ran a movie in the theatre, the next day or the prior day they ran the same movie on TV.
Their newsletter was consistently wrong (e.g. internet available on 3 floors - but in fact only on one). They failed to advise passengers that they were adding a third formal for Christmas so when the last formal night came, many people did not have enough clothes.