From a form perspective, the presentation is clever. Widen and narrow the screen and see what happens, as you make the window narrower, first the infographics move closer to each other, then the design switches from a 2 column to a 1 column layout.
From a content perspective, there is some work to be done. Data is not rounded up and makes it hard to read, and some of the information presentation is not terribly relevant to the viewer (pizzas served). Then, the objective of the site is to show that a lot of stuff is going on at Mailchimp, and with that in mind, they succeeded conveying the message.
P.S.: another cool annual report: Warby Parker (h/t Duarte)