My family and I tried Celebrity for the first time. We had read mixed reviews prior to booking. It seems there are some loyal customers, but those that have cruised other cruise lines, tend to give them low marks. We have sailed on Disney many times (14+), but now that our kids are older, we thought we would branch out. If you have sailed and liked Disney, our advice is to stick with them. Not only do we feel that way, but it became apparent that the crew on the Millennium felt the same way. At the beginning of the cruise, one of the crew members asked if we had ever sailed before. When we said yes on Disney, they hung their head and said "oh, we can't compete with them"!
Here are the good things about the ship: the rooms are spacious and clean. The inside pool is awesome, especially when in Alaska. There is a large variety of shopping on board.
Here are the things to be aware of: the crew are not rude, but are very uncaring. They have a job to do, but don't really want to go out of their way to help. The food is acceptable at best. The photo team are all very rude and will not allow you to take your own photo with their characters. They could all learn a lot from the "Disney Difference".