http://blogs.technet.com/mdop/archive/2009/02/26/get-your-applications-virtualized-on-windows-7-beta-with-microsoft-app-v.aspx

We’ve been listening to customers who want to see us support Windows 7 early so they can move ahead with their application testing in preparation for their enterprise deployments. Today, we are pleased to announce the immediate availability of App-V 4.5 CU1 for the Windows 7 Beta. 

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we are also pleased to announce that engineering of the next App-V release is progressing well, and we will be opening the Technical Adoption Program (TAP) for App-V 4.6 shortly.  When released, App-V 4.6 will be available to all existing MDOP customers and provide new key features including 64-bit platform support.  Customers interested in App-V 4.6 can watch for registration to become available at Microsoft Connect in Q1 of 2009.