What about "Vista still takes 40% longer to execute the OfficeBench test script"? Is that meaningless too?

Usually the reason for one control's class "needing" to know about another control is because of the data stored in the class, and has nothing to do with the control itself. If this is your situation, then consider collecting the key data together in one "data" class, and accessing that class via the CWinApp object (or a global variable).