Having cruised both lines (NCL 3x and Carnival 5x) I think you'll enjoy NCL. It's a different experienc from Carnival - and all the food CAN be included if you want it to be - you don't have to pay extra for the specialty restaurants if you don't want to. But if you want a more specialized dining experience you may decide it's worth it to pay the cover charge and try a couple of the restaurants.
We found that things quiet down a little bit earlier on NCL - which didn't really bother us as we aren't big nighttime party people anyway. There are still plenty of activities offered - many of them similar to what is offered on Carnival. What we miss - the warm chocolate melting cake - the stateroom size -- NCL is considerably smaller, but very well organized.
What we liked - the option to eat when and where we wanted to without having to be on a schedule - we never waited more than 5-10 minutes for a table. We loved the service - the crew was fabulous - and the ship's decor was fantastic. The pools and hot tubs don't seem as crowded on NCL, either. I don't know if it's laid out better or if they're really larger. Also, it seemed that the dining options at breakfast was a little better than on Carnival - but the quality of food at dinner and lunch is comparable across both lines (although if I remember right, the dining room is open on NCL at lunch most days).