There's a new article in the MSDN Library on load testing SQL Server 2005 Reporting Services Report Server using the load, Web, and unit testing tools found in Team System (Using Visual Studio 2005 to Perform Load Testing on a SQL Server 2005 Reporting Services Report Server).
Summary: Microsoft Visual Studio 2005 Team System includes a load-test tool that you can use for performance and stress testing of a Microsoft SQL Server 2005 Reporting Services deployment. The load-test tool runs the tests that you create, and optionally logs the data into a SQL Server 2005 database. You can monitor tests as they progress, review performance data after the tests are completed, and precisely determine what the threshold is for a specific report-server deployment. This article contains step-by-step instructions for creating a Web page load test, and sample code and instructions for creating a unit test. Also, instructions are provided for setting up the load test that you use to specify load patterns. The article assumes that you have the AdventureWorks sample database and reports, so that you can try these steps on your computer. (25 printed pages)