You need to have a group or interest field where to store this data, don't you? with that said - currenty it is not possible. We plan to add a mapping in a future release. Where people could determine the joomla field and the mailchimp fields. So the user won't have to fill more data than necessary.

Exactly, I want to be able to segment my mailing list. It's very important for being able to deliver the highest value messages. Thanks for the response.

By the way, this seems very much like a "Pro" feature. I know I'd be willing to pay $30 for an update that could handle this.