We last took a cruise with NCL a bit over 2 years ago on the Jewel and we liked the experience a lot.
Last year we took a cruise on Royal Caribbean and at the time we thought we would always choose Royal Caribbean over NCL in the future. But, time passed and we found an NCL ship / itinerary / price we were happy with and we jumped on it. After the first day the difference was obvious and we were disappointed we hadn't stuck to our previous decision not to return to NCL.
Worse - NCL has actually dropped substantially in our estimation from our experience 2 years ago.