(When I did, I was given a "sign in with Google" chooser - did you consider telling people what is going to happen before they do that? It might seem obvious, but it might put people off too.)
Also, have you considered per-domain pricing? With the demise of Appointment Slots, this could be something you could sell to a Google Apps for Business customer for all their users.
Per-domain pricing seems very interesting, I will look in to it, thank you!
I was going to try it out on my calendar - with a colleague in mind. I don't schedule enough appointments to make it worth it to me, and I'm not really interested in giving you my CC details just to test it for someone else.
At the very least, you should make the demo link easier to find.
Just because I have availability doesn't mean I am available...