I have been converting a lot of the boxed types in pygtk over to my new PyGBoxed code. So far, this has resulted in about 1000 less lines of non generated source code, which is helpful. It will also help wrap other addon widget libraries that have boxed types (provided they are registered with glib). I will have to submit a few patches for GTK to register the last few types that aren't already registered.
The development version of libglade got support for container child properties recently (thanks to the new GTK APIs from Tim), which means that most container types can be handled by libglade without any extra code, which brings us closer to a stage where no new code would be required to support new widgets. I also started work on a simple converter to go from the old file format to the new one. It still has problems, but it is better than nothing, and should help test my code.