Tina, my family and I just returned from the Sensation last night. I too was very surprised to see how dressed up people were on the formal nights. You definately need a cocktail or tea length dress like you would wear to a formal wedding. and you would not be out of place with a gown. Suits for the men,or sports coat and nice shirt, slack and tie are appropriate. I saw some men with tuxes but more were wearing suits. Lets face it,a guy wih a tie looks very dressed up but a woman with a regular dress on does not. you will have a blast, enjoy every minute.