From my experience Celebrity is the cream of the crop..... I have sailed on just about every cruise line, they all have their pluses and they all have their minuses. However, I don't think Celebrity is worth twice as much. If you can overlook the little things, you'll enjoy a Norwegian or even a Princess cruise just as much. After all, its the cruisers that make or break a vacation. Give Norwegian a try, its worth a least a try. If disappointed, you can always go back to Celebrity, or try another cruise line such as Holland American, Princess, and Royal Caribbean.....
I enjoy Norwegian because of the freestyle dining. I like being able to eat when I want to, and with who. Of course, with open seating you might have to wait 10 or 15 minutes for a table.... To avoid a line, either eat early before 6 PM, or later after 8PM..... Many have posted that there could be a line at 7 PM, but there is a line at your local restaurant on Friday and Saturday nights too at 7 PM.....
As far as formal nights are concerned, with Norwegian they're optional. One of the two main restaurants will host a formal night, while the others host a resort casual attire although the formal attire tends to overflow into the resort casual restaurant.....