I don't think cleanliness is the biggest issue when it comes to shared bathrooms since both men and women can be clean or messy. As a woman I would be most concerned about periods. Some women try to hide when they are on their period for various reasons. If you are sharing a bathroom either everybody will know you are on your period (and the guys would have to be okay with tampons and such) or you would have to hide all of your feminine products which would be annoying.