We sailed on the Celebrity Constellation in June, destination Baltic/Northern Europe. There were five of us total, including my 3-year-old daughter. It was our second cruise, second with Celebrity -- first cruise was a Mediterranean cruise last summer on the Silhouette. Embarkation was a breeze, much faster than last summer in Venice. The ship is a little older and smaller than the Silhouette, but we were very pleased overall. The ship was clean and the staff was very friendly, and very accommodating of my daughter. We dined in the buffet most mornings and ate in the MDR every night except the first night in St. Petersburg. I thought the food in the MDR was even better than Silhouette's, and the service was excellent. Buffet was very good also -- no complaints. We enjoyed the poolside burgers and dogs frequently, also. We did not have a drink package but did frequent the martini and reflections lounge. Recommend avoiding the happy hour specials as the drinks are weak and overly sweet.
Our favorite part of Constellation was the adults-only pool with the bubble seats. We did not use the spa but did use the fitness facility, which wasn't as spacious as Silhouette's and did get very crowded at times. We appreciated that the adults-only pool was open to children at a couple points during the day since the outdoor pools could not be used with the cold temperatures. Our daughter went to the kids club a couple of sea day mornings and she had a really good time -- the kids club staff was great.
Ports: We used SPR for Germany and St. Petersburg and were very happy with both tours. We skipped Berlin and toured Rostock and Warnemunde instead and found those tours interesting. Sweden we went with a Celebrity tour that was a bit of a mess due to our inability to hear the guide 75% of the time. They really need the whisper devices for tours with large numbers of people. For Helsinki and Copenhagen we did the hop-on bus tours and while expensive we felt that we got a good overview of those cities from the bus tours. Be sure to wake up early for the sail-in to Stockholm, it was one of the highlights of the trip.