Is it fair to assume that the "Powered by Happy Cog Hosting" implies Happy Cog was behind the redesign? Potentially irrelevant, but curious.

Regardless, I agree. This seems like a step back. I'm a huge fan of Mailchimp, their brand (well, to date), and the way they engage their users (aka "support"). Mailchimp is known for their ease of use, but this design doesn't reinforce that, especially the overuse of imagery (ref: http://mailchimp.com/features/).

Mailchimp has been known for their transparency (ref: http://blog.mailchimp.com/going-freemium-one-year-later/). I hope they share their decision process on this, or metrics on the new design, or both.