There is not a lot of difference between casual and semi-formal for females for gents jacket/shirt/trousers is still the option for the semi night for us and yes on the casual nights more and more jeans are appearing. I usually take my tux as opposed to my black dinner jacket for the formal nights and even the tux numbers are dwindling to around 5% or less on the last cruise we were on but I still like wearing mine so who cares.
I was on Independence in July and the formal nights are of course very formal. Most people make the effort which is nice. The other nights will be either casual or smart casual. Some people wear jeans on casual nights but some people will still dress up a bit, it's up to you. Smart casual nights people tend to dress up again but just not as much as formal nights. You can't wear shorts and things like that into the dining room in the evening but you can be as casual or dressy up as you like. Hope that helps!
Unfortunatly i found the independance was quite informal when i went to the canaries in may, we went prepared with tux and evening dresses for me but hardly wore them as the rest of the passengers dressed down rather than up!
75% wore tux on formal night I am glad to report on my recent cruise. Everyone else in a suit. Yes,you can wear jeans on casual night, but I think a pair of chinos looks much smarter.
Just been on the independence of the seas 6/09/08 - 20/09/08 formal most adhered to with nice tux or dinner suit but smart casual unfortunately you had some that were allowed into resturant in short sleeve no jacket which we thought was a definate no no and the maitre de should have requested they put on a jacket as this was the dress code of the day. apart from that the cruise was very enjoyable.