At first it was a little hard to start off, just because I didn't realize that I had to create the cart off site. But once I created the Ecwid cart, it was really easy to get going. I haven't used the Paypal API yet, but I am going to configure that later today.
Great product, and I am still shocked that it is free! If you continue to work on this project, and feel the need to charge, I would be more than happy to contribute.