If I have an OptionPage that is in a deeper level of an hierarchical structure the method call DTE.get_Properties("FirstLevelCategory\SecondLevelCategory", "Page1") will fail. It is not possible to get a Property.
Also tested with DTE.Properties[]. Regkeys CurrentUser/Software/Microsoft/Visual Studio/10/AutomationProperties/ properly registered.
Properties of Environment/Documents/ are available.
tested with:
Windows 7 Pro, Visual Studio 2010 and 2013
Greetings
Thomas
Sample Screenshots: