Thanks for taking time to offer feedback. You've run into a few bugs, but given the complexity of this plugin and the modules you are using (Authorize.net) which is not one of our more commonly used gateways, I'm not sure your 3-star rating is fair to the overall plugin itself. Since we've addressed those bugs in Auth.net within 2 days, and one other extra fields bug outstanding you've filed, can you reconsider your rating here? I would also like to point out that two of your original "bug" reports were actually theme conflicts and user errors. So far, I count 3 bugs--2 against Auth.net, and one in the extra fields module for import. One other issue outstanding at the moment could be environmental.
In addition, I challenge you to find a plugin that has responsive support about issues you uncover. The most popular plugins in WordPress frequently ignore their users, but not us.
AWPCP is installed on thousands of sites and does more than about 90% of plugins in the repository in terms of functionality, so I would kindly ask that you reconsider the review if possible.