The GDBusProxy problems I blogged about were fixed quickly thanks to the hard work by Carlos Garcia Campos, Matthias Clasen and others. The GDBusProxy API changes are stable, see 'API changes in GLib master' by Matthias Clasen.
The gnome-3.0 module set is moving to GTK+ 3, and so begins the next round of build failures. GTK+ 3 has removed GdkRegion, to be replaced by Cairo's cairo_region_t. Software that hasn't migrated fails to build: metacity, gucharmap and gnome-control-center. A few modules depend on metacity and gnome-control-center so I can't test GNOME for now.