I just finished a really fun BI POC build. In this POC, I have been using an Excel Power Pivot .xlsx file as a PerformancePoint data source! I was skeptical but hey it works even better that I thought it might. I have PerformancePoint Filters, PerformancePoint Analytic Charts, “slice/dice”, drill downs etc. all sourced from an Excel Power Pivot file that using Tabular data sources versus SSAS OLAP Cubes. It was fast, easy and actually pretty cool. If you want to give this a try for yourself, here is a TechNet link that describes the Power Pivot in PerformancePoint connection string. http://technet.microsoft.com/en-us/library/ff191197.aspx
The key was to create a data source that points to the URL of the Power Pivot file in the connection string: PROVIDER=MSOLAP; DATA SOURCE=http://SharePoint2010Site/DocumentLibraryName/PowerPivotFileName.xlsx
(Note that I did not need the TechNet mentioned hotfix to do this stuff; try it first without that hotfix install hoopla.)
A few things that did not seem to work are Parent-Child Hierarchies in Tree Filter Controls and the PerformancePoint specific Time Intelligence formulas. However, overall it works pertty well.