Does the Lion App Store have a debug menu?
The debug menu is available in the Lion app store, with the same command as you posted.
I don't see any other hidden prefs of interest:
NSWindow Frame Preferences" = "-1 53 1289 1005 0 0 1920 1058 ";
ShowDebugMenu = 1;
WebKitUserStyleSheetEnabledPreferenceKey = 1;
availableUpdates = (
);