The most common question that I received on Beta 1 of this application was about testing with transports other than File. While it is not my intent to write all of the implementations that may be necessary I did provide an extensibility model for the community to do so. However, it was buried in the Help File and not very explicit about how to go about writing your own extensions. Therefore, I have published the BizTalk Performance Tester Extensibility Guide to provide more guidance on how to extend the application.