First the positive. We had the nicest/largest bathroom we've ever had on a cruise ship. We've done 20 cruises on 9 different brands. This was our third on Celebrity, and I certainly wouldn't pick them over any other w/the same or similar itinerary. The main dining room had good, but not exceptional food. They did, however, serve very nice-sized lobster tails on the last formal night. The dining room was only open for lunch on sea days, and the buffet was the usual "mad scramble". The choices were fine, but it certainly is not a relaxing dining experience.
This ship is very large and only has 2 elevator banks. Most large ships have 3. Unless you have a room near the elevators, you constantly walk a long way to get to either stairs or elevator. We tried to use the card room, but frequently found it fully occupied. The design of the ship has both the card room and library open to the foyer below. This allows the loud music noise to spoil your time in either of these places. Very poor design. Also, I have nothing positive to say about the decor of the ship.
All things being equal, I would always choose Princess for a longer than 7 night cruise as they have laundry rooms.
We had a veranda room w/a lifeboat obstruction, but don't hesitate to book one of these as the lifeboat didn't bother us in the least.