We are HAL cruisers and are currently giving Celebrity a try for a few cruises. Millenium is a very pretty ship. No issues with maintenance, everything functioned and there was attention to detail. Meals were all very enjoyable. Martini Bar is very fun, live music was plentiful and professional with something for everyone. Showroom entertainment was typical but fun and worth the time. We had nice weather so the pool was busy and again, well attended to by the staff.
We're poker players and this was the worst poker we've had on a cruise. The electronic table had a very old version of software and the play was very slow. That slow play kills the tournaments as the amount of hands between blind increases is so few, it is not really a valuable game. The live games start so late, usually 10:30 (advertised as 10PM starts) that not many people played.
We felt there was not as much to do during the days as we are used to on HAL but we still had a great time. Planning to try Solstice class for next two cruises and looking forward to those ships.