Advanced Load Testing Features of Visual Studio Team System

Bill Barnett, a Software Design Engineer in Microsoft, wrote a great article on MSDN describing all the bits and pieces of Load Test features in VSTS.

Visual Studio Team Test Edition provides two capabilities that can allow
users to create load tests of web sites quickly and easily: the Web Test
recorder and the Load Test wizard. In fact, these tools make this process so
easy that it is tempting to use the web tests and the load tests that result
from using these tools without much modification. However, to use the web
testing and load testing capability most effectively it is beneficial to
understand how to use other web test and load test properties that are not set
by these tools. This note describes some of the most important considerations
for load testing with Visual Studio Team System that are not addressed by the
web test recorder and the load test wizard.