Now that GNOME 3.0 / GTK+ 3.0 is out in the wild, work on GTK+ 3.2 is beginning to heat up. The latest updates to Broadway on GTK+ Git result in a much snappier experience with eliminating round-trip calls. There's also lots of bug fixes and support for new features, like in-process cut and paste support.
There's also now support for chrome-less browser windows with a canvas inside to support for real top-level windows. Below is a demo of this latest Broadway code.
All of this can be found in GTK+ 3.2 when released later in the year.