3.8: many critical unresolved issues

The 3.8 version is not ready for production sites.
It does some smart things to take advantage of the new WP custom post types and custom taxonomies that give significant feature improvements over earlier versions, but 3.8.4 is not ready for a production site out of the box.

The current status of the Gold Cart authorize.net plugins is a particularly notable step backwards from their formerly functional-out-of-the-box state.

Be prepared to spend many hours hacking away at the core PHP of this plugin to get everything to work as expected.
Explore other options if you have not already committed to this plugin.