Several new API Enhancements have been made for WebTest's in the Orcas release of Visual Studio Team System.  Here are some links to examples:

DeclarativeWebTest & DeclarativeWebTestSerializer:  http://blogs.msdn.com/densto/pages/declarativewebtest-declarativewebtestserializer.aspx

WebTestRequest.DependentRequests Collection: http://blogs.msdn.com/densto/pages/webtestrequest-dependentrequests-collection.aspx

WebTest.Outcome & WebTestRequest.Outcome: http://blogs.msdn.com/densto/pages/webtest-outcome-webtestrequest-outcome.aspx

To find out about more of the new additions to Orcas check out the links in this post: http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1177487&SiteID=1