First, a summary statement: we were very pleased with Millie and had a great time. I think people who write terrible reviews must have had something very unusual happen. Here are my details.
I think reports of Millie looking worn and torn have been overblown. Yes, there were a few areas where she needed work, particularly a) some chairs in the buffet area that looked like they had been through a war; b) the nude sunning area on the top deck that was not in use and was torn up. Otherwise, I didn't notice much. As others have reported, she was constantly being cleaned and maintained - small areas were being constantly cordoned off while we were in port for repairs and maintenance.
Food - we ate in the main dining room just 3 nights because frankly I was just not overwhelmed by the food quality there compared to other dining options. I am a "foodie," and was a huge fan back in the '90s of eagerly awaiting mealtime on Princess cruises because their food was sooo good. In my opinion, food quality on all cruise lines has gone down in recent years. We were at second seating on Millie, and my first night I got the chef-recommended halibut and it was dry and overcooked - I had to send it back. I went for an entree off the vegetarian menu the second night and was more impressed. But generally, eating at 8:30 was too late for me, so we were happy with the limited buffet options - I gorged myself on sushi every night! (It wasn't the best sushi I'd ever had but never tasted fishy.) Chocolate desserts were consistently wonderful, and the Cova Cafe pastries in the morning lived up to their reputation. As a croissant alternative, try the brioche - yum!!
Great mirrors so it didn't feel claustraphobic. Comfy bed. Clean, smelled fine. Great use of space with lots and lots of drawers that I didn't even realize until the last night! Big suitcases fit under bed. Bathroom felt roomy. Hallway very quiet and low traffic.