If you have a chance to go to Alaska then do it!
This was our second cruise in Alaska and we may have had high expections after the first one with NCL but Celebrity did not come close to meeting them. On NCL there always seemed to be something going on while on the ship and beyond eating, sitting by the pool and drinking we found Celebrity had very little to offer that did not cost an additional arm and a leg.
On average the food was mediocre. Dinner at the main seating was above average typically and after changing tables our service was excellent. The first table was bad enough that we asked for a change. Food at the buffet was not very good and the selection was minimal. They had plenty of stations to get made to order things but the lines at those tended to be long and block people form getting to prepared food. Room service was hit or miss.