I use Gravity forms for simple purchases in place of a shopping cart. I would be very interested in being able to integrate my Mailchimp add-on with the eCommerce360 functionality for Mailchimp..
I'm gathering from the API docs that the form would need to be able to accept a couple of incoming parameters and send them back to Mailchimp upon completion of a purchase, http://apidocs.mailchimp.com/api/how-to/ecommerce.php
Thanks for the consideration. :-)