I booked a session not long ago with amazon Nikki, and I was really impressed with her booking method. (she was impressive in other ways too, of course).
She uses "youcanbook.me", and I found it much more convenient then the traditional back and forth with "do you have any openings on this date", "when would you like to see me", "is there anything after 8pm" etc..
With this site she emails you a link and you see exactly what dates and times are open for the specific trip/city you gave her. Easier for her, easier for the client, cuts down on emails.
do other women use this or other similar sites? why do you suppose this isn't more prevalent? The cost seems to be minimal.