Hi Jason,
I am using this plugin with "PMPro Register Helper" and "Theme My Login" and unfortunately it's not adding users to Mailchimp list during registration on WordPress.
I am developer myself and tried to debug where I found that it's making successful API calls and also display the list of Mailchimp lists but the only thing is it's neither adding users during registration nor updating under edit profile.
Registration page: http://learningnow.tv/login/ OR http://learningnow.tv/membership-checkout/?level=1
Mailchimp List: Learning Now tv subscribers
Thanks in advance,
~ Dipak G.