It may well depend on the particular ship but I've been reading some particularly-horrid TRs about the Celebrity Millennium focussing on the poor shape of cabins and horrible food/service in the MDR while the ship was in the east Asia over the past few months. Aqua class passengers report not being able to get into Blu among other things.

Only reason I am considering the cruise is it's a cheap TPAC (<<US$1000 p.p inc. tax, fees and gratuities, about the same daily cost as their Classic Beveareg Package).