I'm using the FREE version, and the PayPal integration has yet to function properly. I click checkout and the page refreshes but never redirects to PayPal?!?!? I sent an email to the author on 8/27, and I received a pretty quick reply, but no resolution. He offered to assist, and I never heard back. I'm hesitate to upgrade because my issue with the free version is yet to be resolved.
P.S. I am, however, happy for the people who are able to successfully use this plug-in. :)
P.P.S. My site is running on the Genesis framework. I'm not sure if that will mean anything to the author.