>However, this doesn't work for all COM objects. For most, if the object is creatable via CreateObject or if you have the type library loaded in the Intellisense Manager (Types - Type Libraries), it will display properly. However, for some (like ADSI objects), it doesn't appear to work.

ADSI (and other object acquired with a moniker/namespace) objects are different from normal COM objects- their available PEMs can be built dynamically and so a normal type-library exploration won't work. There is, however, an alternative way to explore ADSI objects, through their corresponding Schema object, which lists optional and required properties.