I think with cruises starting in May there will be no more informal nights. The dress code for formal night has also been changed to allow men to wear a sports type jacket instead of a dark suit coat. However, a tie will still be required with the jacket.
I think the dress codes are being simplified due to the luggage limitations being imposed by just about every airline, and the difficulty encountered when trying to pack for three different types of evening requirements. These new requirements eliminate the need for men to bring both a dark suit for formal night and a sport jacket for informal. Now one can serve both purposes, and certainly the tie won't take up much room in the suitcase.
As for women ... personally, I never saw any difference between casual and informal nights, and I pretty much dressed the same way for both. All the new dress code means is that I can now "officially" do that.
Blue skies ...