@The Jimmo, I have some questions before purchasing:
Can I have a block on my site for Guests to subscribe to newsletter without registering with my site?
Can I differ members (sync from IPS) and guests (subscribed directly) in Mailchimp list?
If Guest subscribes to Mailchimp first, and then decide to register with my site, will your app update the entry in Mailchimp with newly registered user?
What happens if the user uncheck receiving admin emails in his profile on my site, will the e-mail be deleted from Mailchimp in this case?
What happens if the user chose to receive admin emails later, will the e-mail be added to Mailchimp?