Hi,
Found these helpful articles while looking for improving the performance of one of our reports.
- http://msdn.microsoft.com/en-us/library/bb522806.aspx
- http://sqlcat.com/sqlcat/b/technicalnotes/archive/2009/01/14/reporting-services-performance-optimizations.aspx
Also check this video from Channel 9
http://channel9.msdn.com/Events/TechEd/Europe/2009/DAT306
Bye.