I've sailed NCL, Princess and MSC.
Like MSC, I didn't go with high expectations based on reviews. The trick is to go with low expectations and then you won't be disappointed!
The truth is you can't pay Costa money and expect NCL quality. Value for money wise - I thought it was very good.
I had booked an inside but got upgraded to an outside cabin. It was also an accessible cabin so much bigger than normal cabins. Cabin was of good quality and very clean. Very happy with stateroom.