Since the Solstice Class ships came on line we've done nothing but, 9 cruises overall on those ships.
Millennium was just refurbished the week before and everything was 'new'. There are many Solstice-like features incorporated into this ship which is generally a good thing.
There were a few oddities, like a club for the suite guests in the middle of the shopping arcade, that never had more than 2 or 3 people in it.
We had unfinished walls - insulation showing and black marker writing on doors, leaking shower stall resulting in wet bath floor, sink that didn't drain, broken 'couchette', exterior door that didn't seal properly, air vent that hissed like a jet taking off, and rodent dropping behind nightstand.
Housekeeping management was appropriately mortified and we had a procession of technicians in the room over ten days to address all the issues. side note: having a parade of strangers in your room isn't quite the Celebrity experience we are used to.