I'm messing around with the Notebook widget and there doesn't seem to be a way to see the tabs as tabs. The tab text and the blue 'selected' indicator show up, but the actual graphic treatment of tabs doesn't.
I've seen this in the PyGTK demo, but isn't it possible in GtkD? I checked the demo you wrote for the package and it's graphically the same as what I'm getting. Here's the PyGTK demo I'm referring to (you'll have to scroll to the bottom to see the screenshots).