Does gtkmm force STL-style interfaces onto GTK+ widgets in a way that is inappropriate, difficult, or badly-implemented?
No, we do not force you. We have provided STL-style interfaces for some container widgets, to allow you to iterate over the child widgets, but these are in addition the the simpler interfaces. We have done this because we believe that STL-style interfaces sometimes require too much code to perform simple tasks. On the other hand, some people religiously prefer STL-code wherever possible. You have the choice. These STL-interfaces are implemented with quite simple code and have been found to work without problems. There are no known bugs, as you can see on the bugs page. Some classes such as Gtk::TextBuffer have only an STL-style interface. This is because the underlying widget has an STL-style interface, implemented in C. So this is the most appropriate, and easiest, way to wrap that API in C++.