Hello Lunatic-Mic,
Have to admit that I've not been on an NCL cruise, but people on these boards have discussed it plenty, so I feel I can answer your question.
Apparently, on a Norwegian Cruise Line ship you are not tied to a specific dining room , nor to a specific time for your meals. Of course you are familiar with the Lido deck offerings on your Carnival and RCI cruises. On NCL, in addition to that there are several dining rooms to chose from. Like one Italian, and one steak house, etc. (anywhere from 5 to 7 or more choices, from what I understand.)
You can choose to eat at any of those dining venues, at whatever time you choose. That's the good things. The choices.
Here's the bad thing, of those several choices, only about three or four of them are "cost included". All the rest cost you additional money $10, $20 ? it varies. (Perhaps someone else can step in with more exact prices for you here)
Also, most of the restaurants, (all except about three of them) require you to make reservations in advance. Getting the reservations at the time you would like to eat may, or may not be difficult. I have read reviews that state both ways. I believe the difference is probably in that some times are more popular. If you like the less popular times, you will think getting the reservations is very easy. And visa versa.
Also, some have complaint of having to wait in lines at the venues that do not require reservations. Again the time you choose to eat will make a difference in your experience.
One more thing, if you like to attend the evening shows, you will have to arrange your meals accordingly. On ships with traditional dining, the shows are planned with the meals in mind. You can be fairly certain you will be out of dinner in time to attend, every night. If you end up waiting in line for your meal, or just happened to eat at an off time, you can easily miss the show.
One more thing, if the personalized service is important to you, you cannot expect that kind of attention when you have a different waiter every night. They will not have any chance to know your likes and dislikes.
Also, dining in a different restaurant each night, means no regular tablemates. That is good or bad, depending on your preferences. I would miss the camaraderie. You can choose to eat with other tablemates at the freestyle dinners, but you will meet new people daily. (And probably have the same conversation everyday: example: "Hello, my name is xxx. We're from Ohio. where are you from? Is this your first cruise? what ships have you been on? " Repeat the same tomorrow with new people.)
About the dress code, I really don't know if they have formal nights or not. I think not, but otherwise, I think you still have to dress nicely. (no jeans or tees, etc. ) Perhaps ask that in a separate thread, and someone with experince on NCL can tell you for sure.
Some people love this system, others do not. I haven’t tried it, but I think I'm likely to be one of those who do not.