My husband and I sailed with Norwegian for our honeymoon, and had a wonderful time. We had a mini suite which I highly recommend because you get concierge service, and we took advantage of this more than once (dinner reservations, shore excursions, etc..). Plus the balcony was wonderful to eat breakfast on!
We enjoyed the food onboard and tried most of the speciality restaurants. We really liked Endless Summer. We liked being able to eat whenever we wanted, and to have the option to eat alone. Also, they will save your wine for another night if you don't finish it.
I recommend booking all of your shore excursions before you cruise (which we did), because the line for them looked long. We also really liked our trip to Fanning Island. It was a once in a lifetime experience. We booked the excursion to the private beach, and it's well worth the extra money. It was the most beautiful beach we have ever seen, but make sure you head to the other side of the island for the BBQ.
We enjoyed the days at sea it took to get there, but after planning a wedding I think we were looking forward to the down time! My personal favorite for days at sea were lying by the pool with a Mai Tai.
The entertainment on the ship was pretty good. I especially enjoyed the Andrew Lloyd Webber show. We didn't feel formal night was worth the effort or expense. You spend most of the evening waiting in line for picture to be taken, but to be fair we were tired of our picture being taken, and we had recently been all dressed up (remember the wedding!?!). So maybe it was better than we thought, who knows.
The spa on the ship was great. I had a massage, and only wish I could have stayed longer! Overall, we thought everything was great and would sail with Norweigian again. A wonderful way for you to get a taste of Hawaii, especially for first timers. We stayed in a hotel on Oahu after the cruise and thought that was a great way to wrap up the trip. The Halekulani on Waikiki beach is a fantastic hotel, and I can't say enough good things about it.