Having sailed with Princess primarily, in comparison to Celebrity these are the highs and lows:
Celebrity Pros:
Newer ship (solicitized in Feb 2012)
Aft-Facing Balcony. It is quite large; about 300 sq. ft., and the balcony is approximately 250 sq. ft. Noise from the restaurant/bar was noticeable when standing at the railing, but underneath the canopy it was not noticeable. We did have some trash accumulate over the sailing; mostly straw wrappers, and one cigarette. The bed and pillows were comfortable, better than Princess. Room furnishings were new. Concierge Class does not seem to be worth the extra money, except for the aft balcony which was outstanding. Location was also good with rooms above and below, yet close to dining rooms, the sunset bar, and fairly close to the pool.