The following links may be useful for people wanting to know more about how to test their application with Visual Studio 2008 Test Edition:

Using Fiddler (www.fiddler2.com) to record VSTS web Tests
http://blogs.msdn.com/buckh/archive/2007/04/18/vsts-testing-using-fiddler-to-record-vsts-web-tests.aspx

What’s new with web services in Silverlight 3 Beta
http://blogs.msdn.com/silverlightws/archive/2009/03/20/what-s-new-with-web-services-in-silverlight-3-beta.aspx

Debugging Web Service Usage in Silverlight 2
http://blogs.msdn.com/silverlightws/archive/2008/04/16/debugging-web-service-usage-in-silverlight-2.aspx

The other way to see how your application scales is to write unit tests to test your Web Service facades. See the following article: Testing Web Services http://msdn.microsoft.com/en-us/library/ms243399(VS.80).aspx

Visual Studio Test 2008 Test Rigs
http://msdn.microsoft.com/en-us/library/ms253092.aspx

Tips for Recording Web Tests with Team System 2008
http://msdn.microsoft.com/en-us/library/cc678655.aspx

VSTS 2008 Data-Driven Web Tests
http://www.jeffreyhunsaker.com/2009/01/vsts-2008-data-driven-web-test.html

A really good video to see VS Test Edition capabilities can be found here:
http://www.asp.net/learn/vsts-videos/video-128.aspx

patterns & practices Performance Testing Guidance for Web Applications
http://perftestingguide.codeplex.com/

A very comprehensive book on Visual Studio 2005 Test Edition that is now at bargain price.:
Professional Software Testing with Visual Studio 2005 Team System- Tools for Software Developers
[Note: Even though it’s focused on VS 2005 Test Edition, a lot of what’s covered in this book can be carried over to VS 2008 Test Edition.]

Excelsior!