I really like formal night, but one on a 7 day cruise is enough for me. As for the "categories" of dress I see people in a variety of styles on each night from casual to dressy no matter what it's supposed to be. Formal nights, people do make a little more effort, but I still see dressy casual on those nights. I wouldn't miss dinner in the dining room because of what I had to wear, only due to my children's lack of being able to sit through a lengthy dinner or being too tired, then it's off to the buffet. I have never worn a gown on formal night, I have no use for one and can't imagine packing it, but a dressy cocktail dress is useful for other ocassions. My vote would be one formal/dressy night and the rest dressy/resort wear. My DH and I really enjoy the dining room on cruises and on the nights that the children dine with the youth counselors and other kids, it's heaven, it's one of the few times we can relax and just enjoy each other's company.