As a free plug-in, this is great. As a paid plug-in, not sure.
I decided that I wanted the advanced functionality and bought a lifetime license. Right off the bat, I had a question and submitted a support ticket. It has been two weeks and they have not even marked the ticket as read. I tried finding another way to contact the support person/team, but the only way is a ticket (and the ticket is not answered).
As a free plug-in, this is fine, as a premium plug-in, just be sure you won't have any questions. I don't even see a way to refund this plug-in within the refundable window without being able to talk to someone. Perhaps my problem/question is really easy to answer, but I don't know because of no response.
Pro tip to all, don't buy any plug-in without ample contact methods available.
-- Update Jan 2022.
So, I never got any response from my support questions 6 months into having paid for the plug-in, but I did get an email from support because they were changing things. Apparently, I bought a LIFETIME license and they will only honor the LIFETIME license for 1 year. I paid excess money for a LIFETIME license, yet I am only getting a year. It would have more financial sense to have me only pay the 1 year fee. They totally just pocketed the extra money. I do not trust these people; I do no recommend you do either. It is not a safe idea to build your appointment based website off of a company that will not stick to it's word.