Thanks for your speedy reply! I can't deactivate my other MailChimp plugins. I'm using the MailChimp embedded code sign-up form (a temporary solution until MailChimp fixes issues with the MailChimp List Subscribe Form plugin). I'm also using the MailChimp Archives plugin. I need them both.
Instead of your plugin, I'm using the AutoChimp plugin together with the Register Plus Redux plugin, which adds custom fields to the account registration form. It's not a perfect solution because some of the features I want aren't working properly. Specifically, the only MailChimp field which it updates during registration is the email address.
Your CRM approach has tremendous potential. I'm very interested in what you're doing. If you can fix your plugin, that would be a huge help!
Thanks very much,