TimeTap is a fairly mature appointment scheduling application, with the web.archive.org showing website versions as early as 2012. Catering to many industries of scheduling from fitness to enterprise scheduling, TimeTap does seem to be feature rich, and their backend administration has a nice walk through step by step process. However, the backend is symantically very difficult to parse and intuitively use. The front end booking app is really slow however and at the time of writing this article did not even work on their sample pages. The booking page also looks to be designed in a clunky way and looks like the skinned version on the cronofy booking system.
Overall the TimeTap scheduling can be an ok system once users learn how to use it and have a very specific set of requirements that they can provide.
The above feature comparison was performed by our users who were TimeTap users, and may not be 100% accurate. If there are ammendements that you find that need to be made or if you want to confirm the existence / non-existance of certain features please contact us on firstname.lastname@example.org.