A big feature of WebKitGTK+ 2.2.0 is initial support for Wayland when compiled with GTK+ 3.10, but not all Wayland functionality is implemented yet, but it's enough to get running under a Weston compositor while even supporting WebGL on Wayland.
Another win for WebKitGTK+ 2.2 is hardware-accelerated video compositing by using GStreamer with OpenGL acceleration. WebKitGTK+ also has a new web inspector that was contributed to upstream WebKit courtesy of Apple.
More details can be found by the webkit-gtk announcement. Besides WebKitGTK+ having a demo browser/application, this GNOME component is used by the Epiphany web-browser, the Midori web-browser, the OLPC project, the Evolution email client, Gwibber, and many other applications.