I was testing this myself yesterday without luck, but it looks like App-V does not currently run on Windows 7.
App-V 4.5 is not currently supported or functional on Win7. Info on Win7 support will be published soon.
App-V 4.5 will install successfully on Windows 7 x86 and you can load an application into the cache; however you will run into some issues when launching virtual applications. Interestingly, VMware ThinApp also has issues on Windows 7. I would expect all of the application virtualisation vendors to have support for Windows 7 in time for the release.
My recommendation would be to test your applications running natively on Windows 7 before attempting to run them virtually on the new platform – application virtualisation is not a compatibility layer.