I use Schooldude to schedule classes in my Learning Center (library) primarily during the day, but a small amount of evening/weekend hours.
My main concern is the user interface that teachers see when scheduling appointments, especially in the mobile platform, but in general as well. It would be so much simpler if the teacher interface was a calendar view where you could simply hit a plus sign or some other signifying link to take you to the appointment page.
For my purposes it would also be useful to have the day divided into slots. I can fit two classes in my space. If I had correspondingly two slots per period I could then limit the number of people who would be able to send me requests. As it exists, I sometimes receive more requests than I have the space for. Teachers are busy and don't have a lot of time, so they often come before I have had the time to approve their request. If I had a limited number of slots, they wouldn't even be able to make the request.