A PerformancePoint Planning white paper has recently been published that documents the performance and scalability of Planning Server.
Included are some very interesting test results that will come in handy when planning the deployment of PPS for a large number of users. There are also a few tips for the Excel add-in and configuration of the Planning Server.
The following page contains links to both the new Planning white paper and also to a Monitoring white paper that was published a while ago:
http://technet.microsoft.com/en-us/library/bb660521.aspx
