I own the product and I use Clickbank as my payment processor. I did this because I want affiliates and do not want to deal with tracking sales for them.
As far as the autoresponder.....It does not have all the features as Aweber or some others. It is very simple but effective. This landing page software is designed for newbies or people who do not have much background in landing page design.
You can integrate other email companies with Prime Landing Page however...but if you just want something simple to capture leads....this is what it does.
I did it this way because so many new affiliates get into Wordpress and get confused...or spend money on themes and then their product does not sell or they bought into lead pages and went broke because they charge like $40 a month plus money for each template....i thought this would be a nice simple and cost effective tool for them to use (and the hundreds of people using it think so as well)
Best of luck!
Ryan