I think for the most part the pleasure to the wearer is not directly sexual, just pleasing and possibly erotic. Some women (most?) like the role reversal, and being able to fuck a man can be an appealling thing, as long as they can get past the strangeness (and the potential "ickyness").

The pleasure for the receiver can be sexual as well as a submissive feeling. I have personally experienced a dry orgasm from anal play with my cock being rubbed, can't remember if I've ever had one without any such stimulation. An interesting experiment for the future perhaps (I wish!)

Whether a woman gets any direct stimulation depends on where the strap-on is. I think simply pounding away while wearing one won't do very much, but a vibrator makes pleasure for the woman possible, as long at it sits in the right place and stays there.

Hope that helps, and I hope one day you get fucked in the ass, db ;-)