There is now a hot fix available at http://connect.microsoft.com/VisualStudio/Downloads/DownloadDetails.aspx?DownloadID=15510 for the bug introduced in VSTS 2008 SP1 where think times were being ignored during a load test for Web test requests that resulted in redirect responses (described in my earlier post: http://blogs.msdn.com/billbar/archive/2008/08/04/bug-in-vsts-2008-sp1-causes-think-time-for-redirected-requests-to-be-ignored-in-a-load-test.aspx).