On paper they look like great cruises.
I suspect you have see the many newspaper articles on the problems NCL is having with it's American flagged ships in Hawaii. Cruise Travel magazine just did a big story too.
The heart of the problem appears to be the combination of an American wait staff, and automatic, mandatory tipping. Of course, with Freestyle cruising, pooled tips are about the only way it can be done. I guess the original policy in Hawaii on NCL had been they billed you $10 a day for tips, and it could not be adjusted down on the American flagged ships.
According to the articles, several times NCL ended up with very angry passengers, and very bad service....and HAD to refund tip money to passengers....and in some cases, part of their fare too.
My mom has cruised with them since they went Freestyle, but not on any of the American flagged ships (I think they have 2 now). On the non-American flagged ships, they will lower the per day tip, but only if you ask, and only if you got to guest services everyday to lower that days tip. My mom felt $10 a day was excessive since she always eats in the buffets for all her meals.
Myself, at least for dinner I prefer to have the same wait staff everyday, and I prefer to tip them based on their service. I've never tipped less than the minimum suggested amounts because the service I have received has always been great.