Check it out on Microsoft download : Microsoft Deployment Toolkit (MDT) 2008 Update 1
Quickly reading the release notes, here are the new features :
There's also bug fixes in this release and revised docs.
Additionally, the Microsoft Word documentation is no longer a part of the download. Whole documentation has been included as a CHM help file.
If you want the documentation as separate files : MDT 2008 Update 1 Guidance.