My wife and I were on the February 2, 2013, Celebrity Century 15-day cruise to Hawaii. We found the food and the entertainment to be more than satisfactory. As for service, there is about one employee for every two guests, so there is help at every turn. And the ship's physical conditions we found superb. It may be a bit aged as a vessel, but it still has a feeling of luxury.
There is one main dining room with two levels. There are two seatings. Plus, of course, there is a buffet that is open pretty much all the time. You can definitely eat all you want, and we found the food and service to be very good. There were three "formal" nights on the 15-day cruise.
I'm an entertainment buff, so I was very pleased with the quality offered on The Century. It was the best, overall, that I have found on a cruise. First off, there was an excellent house band that backed some of the shows, plus played in other rooms for dancing. Second, there was an excellent "party band" that really had the energy to keep playing when there was a crowd of dancers. They were excellent. But my favorite was The Celebrity Band, which was a group of four from the Ukraine. The keyboard player and the singer were superb, backed by fine drums and bass players. They did jazzy dance tunes that really swung. I never tired of listening to them. On the main stage, the ship's team of dancers and singers did very challenging stuff that we thoroughly enjoyed. They were a treat. The other entertainment was of less quality in my mind, but there was a nice variety of comedians and singers/magicians that, for the most part, were worth seeing. The shows were not crowded on the cruise we took. The one theater was more than adequate in its capacity.