I've seen a number of requests to add a "silent" switch to the ThinApp AppSync.exe utility. Well, a completely silent AppSync can be performed using the ThinApp SDK. This script takes the name of a ThinApp primary data container and a URL as parameters, just like the AppSync.exe utility. It will perform an update (if there's an update available), the only feedback is via its exit code:
0 - Package was updated 1 - No update available 2 - Error occured
Since this is based on the ThinApp SDK you'll obviously need ThinAppSDK.dll/ThinAppSDKSrvr.exe present and registered (using regsvr32) on the system.
It shouldn't be difficult to extend this sample to run AppSync on a whole directory (or directory tree) of virtual apps.