I like to use them, but I am in an area that my stand stays up year around, so after the deer see the skirt blowing in the wind for a while, they get used to it, and it doesn't bother them.
If you are going to hunt an area, and you put your stand up the night before the hunt, I think the deer would come closer to being leary of them, because of the sudden change to their enviroment.
I try to get all my new stands up for at least a month before season, so that there is nothing different to them opening day, but in some states or property, it is not legal to leave your stands up.