There is a new technical document available to download: Forefront Online Protection for Exchange(FOPE) Microsoft Office 365 Beta Documentation.
Office 365 Beta documentation: This download includes the documentation for the FOPE connector features available to Microsoft Office 365 Beta participants. It also contains information about known issues with this beta release. For infomation about participating in the Office 365 beta, see http://go.microsoft.com/fwlink/?LinkId=206771.
One nice chapter that I strongly recommend is the Outbound Smart Host Scenario (also available online), a feature long time requested by organizations using hybrid deployments of Exchange (Exchange on-premises + Exchange Online).