One of the main concerns for PowerPivot as an IT Professional or Database Administrator is that PowerPivot involves many different systems of SharePoint, Office, and SQL Server 2008 R2. It also has a lot of moving parts and making sure that all of these parts work together can be daunting. To help prepare for this, SQL Server and Office beta programs worked to understand the difficulties and issues customers had faced from usability to installation. Microsoft created a whitepaper Microsoft SQL Server PowerPivot Planning and Deployment. In addition to the fact that this paper contains architecture and design information, hardware requirements, topologies, PowerPivot / SharePoint service associations, storage requirements, and deployment planning. PowerPivot is an amazing new Self-Service BI tool spanning Excel, SharePoint, and SQL Server 2008 R2.
More info: SQL Server Technical Article