A new deployment guide was published on Windows7 BranchCache.
It covers the PKI requirements for this feature along with other deployment procedures.
The full guide can be found here:
BranchCache Deployment Guide for Windows Server 2008 R2 and Windows 7
For the most current information about BranchCache, see http://technet.microsoft.com/en-us/library/dd996634(WS.10).aspx