Mutter, GTK+ Advance For GNOME 3.4
GTK+ 3.3.4 drops the Beagle search back-end, the HTML5 Broadway back-end has initial support for V7+ web-sockets, theming improvements, numerous accessibility improvements, and multiple Mac OS X and Windows improvements. There's also plenty of bug fixes.
For the Mutter window manager, settings have finally moved from GConf to GSettings, new window options, and various fixes.
You can find the Mutter release announcement with complete change-log here or the GTK+ 3.3.4 announcement.