Regardless of how users feel about Facebook's new Timeline interface for Pages, developers will have to deal with the updated features soon: Facebook has announced that all Pages will switch to the new design on March 30, 2012. As of last week, Facebook has also added APIs which developers can use to interact directly with the new Page data.
Facebook's official Page API documentation doesn't point out which APIs are new, but the "Introducing New Facebook Pages" section of the Facebook Help Center describes the new design features and how they work. Three major API updates involve messages, milestones, and the all-important cover image.
Cover images display at the top of a Page in a larger size than other photos. They're intended to brand a Page, so users get a good sense of what the organization does; Facebook requires cover images to be at least 399 pixels wide, and the UI will automatically resize a cover image to 851 pixels wide by 315 pixels tall for display. The Page API supports setting a cover image with a simple HTTP POST, after you've uploaded the photo you want to use for the cover.
Milestones are important events which display in the Timeline as larger, more prominent blocks than other posts on a Page. The Milestones API allows developers to Read, Create, or Delete a milestone, and to set any date when creating the milestone event.
Messages are private communications between individual Facebook users and the administrators for a Page. The Messages API lets admin Read messages and Reply to them using an external app. (Note that in addition to the normal Page Access Token required to access a Page, reading messages also requires the read_mailbox permission.)
Complete Documentation for the new Page API is available on the Facebook Developers web site.
(Hat tip: Inside Facebook)