This could be a very promising extension if this developer didn't stop on fixing the bugs. I see a lot of free extensions which developers provided a much better support and thus give you the opportunity to extend the extension by buying some extended versions but this one's not. You must pay for a base and pro version which are not ready to go after installing. You must track the bags and then be sure when everything is Ok to start using it live. One more thing I can't understand is why is this payed extension limited to one site only or 3 sites if payed more, if you must fix bugs by yourself or paying this developer extra for doing it for you.
I strongly recommend to this developer to test the extension on different templates and such, to be aware of bugs and fix them before continuing to sell this buggy extension for $80 + $50!