Linda,
I know what you mean about the holiday cruises. We had to take our honeymoon after our actual wedding (which is in about a month), because my fiance's a teacher, so we're going over Xmas break, and I know it's going to be packed. That's why I'm glad to have the romance suite and our own private balcony. I don't want to fight for space!
The one thing I have heard about holiday weeks, at least for Christmas, which I'm sure is one of the busiest, is that it's best if you don't mind eating either early (5:30) or later (9:30) because it's pretty busy in the restaurants. I thought that was perfect, we like to eat late. Someone also mentioned that it's also good sometimes to get appetizers at a smaller place (like Las Ramblas, on the Star) and then eat dinner.
Just a few things that might help, if it is busy for you. I know I signed onto NCL's site, and did the "Voyages and Pricing" thing just because after a few steps, you can see how much is "booked" for the cruise, ours is filling up fast which tells me it'll be busy.
I've also be told by NCL that with the penthouse/romance suites, you get priority tender tickets, if you have to tender rather than dock anywhere. This is helpful too!
Amy