The WHDC folks now have web page setup for the Windows Performance Toolkit (aka the 'xperf tools'). The page includes downloads for updates to the versions that ship in the SDK. In the near future, this page will include pointers to updated documentation, and discussion forums.
The next article in this series is Using Xperf to take a Trace (updated)
This page included downloads for V4.1.1 of the Windows Performance Toolkit. This download is an updated for the SDK version and includes fixes for two small bugs in the version included in the Windows SDK.