Also, I note that plans for GTK+ 3.0 are afoot. It seems that mostly GTK+ 3.0 will remove some depreciated features. Does anyone feel like testing if synfigstudio builds and works with CFLAGS="-DGSEAL_ENABLE -DDISABLE_DEPRECATED"?
I think by defining those variables with GTK+ 2.X you can check if the code uses any deprecated stuff. Not sure if GTKmm has something similar though.
We can use the glade GUI application and GtkBuilder now, the gtkparasite thing just means that it is much easier to migrate the existing UI to GtkBuilder.