White papers are always good benchmarks of PerformancePoint, however, there are also several case studies of customers with cubes containing billions of rows of data. 

The live demonstration can be very appealing, especially to customers who have been using alternative BI tools. Have a look here:

 http://RichardLees.com.au/sites/Demonstrations/ 

 http://RichardLees.com.au/sites/Demonstrations/Shared%20Documents/Windows%20Performance%20Monitor/Dashboard%20-%20Last%2060%20seconds.aspx

The latter is a dashboard sitting on top of an OLAP cube that has over 100 Million records, and there are about 500 new records every second!  The new records are processed by SQL Server Integration Services every 180 seconds (that's about 100,000 every 180 seconds) and incrementally added to the cube, so that you are always looking at a cube within 180 seconds of real time.