Patrick Azzarello (program manager in the Windows Core Operating System Division) just posted a blog entry listing the deployment-related changes in Windows 7. Check it out at http://blogs.technet.com/windowssystemdeployment/archive/2009/01/20/windows-7-deployment-changes.aspx.
We’re working to integrate as many of these as we can into MDT 2010. Some (e.g. DISM, Windows PE 3.0, USMT 4.0 hard links) are already done in MDT 2010 beta 1, which you can download from http://connect.microsoft.com if you haven’t already done so.