Love this product. I did want to make a suggestion for the next update if possible.
My users' most common complaints have to do with the update registrations element
Editing the billing information is pretty straight forward. It is when you try to "Edit Group Members," the process loses its intuitiveness.
Just a couple of thoughts that might help direct things along...
The "Edit Group Members" link needs to be more prominent on the billing page. Perhaps a button with an optional text link.
There needs to be some direction once you get into the "Edit Group Members" link (like some direction buttons on the bottom, such as "Next Member" and "Back to Billing Info" and "Finished Edits" ...etc.).
To include some basic instructions that are editable might not be bad either.