Here is the list of What's New in PP3 for Windows Home Server.
Windows 7 Libraries integration
When you install the Windows Home Server Connector and log on a computer running Windows 7, you can access the Windows Home Server shared folders from the Windows 7 libraries.
Windows 7 Action Center backup warning suppression
After you install the Windows Home Server Connector to enable the home server backup for your computer running Windows 7, you can suppress the Action Center warning reminding you that Windows Backup has not been set up.
Windows 7 power settings
You can configure your computer running Windows 7 to wake up at a scheduled backup time and then go back to sleep after the backup finishes.
Console support for Windows 7
Windows 7 is properly displayed as the operating system shown in the Computers & Backup tab.
Windows Search 4 is included to improve query search times, indexing times, and reliability. Extended Remote Discovery increases the efficiency of searching across all your libraries running Windows Search 4. Files encrypted with EFS are now supported.
Windows Home Server can automatically archive recorded TV by moving your recordings from a Windows Media Center computer to your home server in the format of your choice. This enables playback in the correct format for your home computers and/or portable devices.
You can view information about your home server’s storage space, hard drives, backup status, and more from Windows Media Center.
Complete details are available in the Power Pack 3 Release Documentation.