The warning from mailchimp is as follows:
Your MailChimp account is using the login() API method which will be disabled in the near future.
I hope the developers can patch this module to work with the new API calls, as it is by far the best mailing list module!
Please make sure you're running the latest version of the module. It uses the current MailChimp API (version 1.3) and also supports both Joomla 1.5 and 1.7, so it should be nowhere near end-of-life.
I have been using joomla for five years and have never had so many problems with one extension. The thing isn't even coded in MVC which turns quick design fixes into painful hours of searching through hundreds of PHP files in order to add an HR or change a font.
Support seems limited on their forums to other users, most of which are so tied up bending over backwards to get their installation working properly they aren't able to help you.
If you're used to how Joomla since 1.5 is SUPPOSED to work, this template will only infuriate you and cost you lots of extra hours while you fix the (sometimes well known) bugs.
STEER CLEAR BIG TUNA - HEAD FOR OPEN WATERS!