The issues we have had with online booking is either one of twofold:
1. You end up telling everyone when you are in sessions or NOT in sessions. So people can see how busy of a therapist or how busy you are NOT. This is not good for many reasons. This happens because if a client CAN pick a certain time, then that tells them that time is open. So if they can pick anytime on any day, that tells them you not very popular. If all times are booked, that tells them and the IRS how many sessions you are likely doing and that's not good either
2. If it doesnt show when you are booked, as some systems dont, then what value does it provide that a simple free "request appointment" form couldnt achieve? All those bells and whistles are great, but the "idea" of online scheduling is much more practicle than the reality of it. In the end, we would have to call to verify the appts anyway, so a simple appointment form works for us.