I always still like to get dressed up on the formal nights, although not in a tux. For my upcoming cruise, I'll probably be in a black 2 piece suit for the formal nights.
On that note, I did have one question regarding etiquette about that. On the formal nights, is it okay for me to remove my suit jacket when I sit down to eat? This is something I'm not always sure about, and don't usually remove it until I see other guys do it, so I'm not the only one.
2007 - Majesty of the Seas (Bahamas)
2009 - Enchantment of the Seas (Western Caribbean)
2010 - Freedom of the Seas (Western Caribbean)
2013 - Golden Princess (Alaska, roundtrip from Seattle)