We enjoy NCL immensely.
It has Freestyle dining and no traditional dining but you can always book the same table and time each night if you wish.
There are several dining options outside of the MDR, some are free, some are paid for specialty dining.
If you get the free at sea package that is usually offered, it is good value, drinks, specially dining, wifi, gratuities, obc and shore excursion money.
The entertainment is good and on the larger ships, it is great as they have full on broadway shows.
It also tends to be a younger crowd than Princess.
I would rank NCL better than Royal, on par with Princess and lower than X in terms 9f overall cruise experience.