http://learngtk.org/what-is-introspection.html
So, what is Introspection? Introspection looks at the version of GTK+ installed on a machine and compiles PyGObject (or other low level library) to make the widgets available which the installed version supports.
Т.е. эта фича нужна, только если пользуешься биндингами типа pygtk?