We did the 12 day cruise starting from Barcelona and had a great time. We had not been cruising on this scale for many years so can not make a comparison with other lines but it felt almost perfect to us.
Our stateroom was a mini suite and bigger than I expected, though the balcony was hard to move around without risking falling over the side. The huge sofa and second tv was great for watching movies when we wanted to get away from it all.
The ship is huge and we frequently got lost in the first few days. We tended to use the stairs so the lifts weren't really an issue for us. The ship was spectacular, especially the central piazza which functioned as a hub of social activity and on formal nights it was great to hang out there and see and be seen. The main pool area tended to be crowded so we spent most of our time on deck in the adult Retreat area, which was nice and quiet. There were some quiet spots on deck seven. It was rarely difficult to get seating despite the huge number aboard. The seawalk was fun, though I would not like to have had one of the stateroom balconies below it.