I would love to see a way to change the button text and add a pre-text message inside the module setup but I can't fault you for wish list items.
Great work & thanks!
Hi, we're glad you're enjoying the extension.
You can change your button text by editing the module's language file for your language.
After the module is installed, you will find the default (English) language file at /language/en-GB/en-GB.mod_mailchimp2.ini
Change the text in quotes to your new value.