Other problems with PDC:
The PDC payment gateway is slow and clumsy
Paypal has too many steps, this can scare off impulse buyers
You have to manually pay your affiliates
You have to manually transfer money from Paypal to your bank account
Since switching to Clickbank, my customer emails have gone down. With PDC, people weren't making it to my thank you page, presumably because the Paypal interface just isn't that intuitive when it comes to returning to the merchant. Not only is the Clickbank payment gateway fast and reliable, users are taken directly to the form to enter their credit card information (no chance to get distracted or scared off). With Clickbank, you don't have to make affiliate payments, as they are handled automatically. After three paper checks, you can set yourself up for direct deposit to your bank account. Clickbank allows you to have a truly automated business.
I'm a lazy guy, and switching from PDC to CB has made running my business much less time consuming.