Because the boys of Xfce they will not carry Gtk3 the version 4.12 of this Desktop Environment, Simon Steinbeiss, the creator of the theme GreyBird, has decided to make some changes to the appearance of it, and work only on Gtk2.
The official announcement was made in the blog of Xubuntu and from what is seen in the images, things look good. Look how it looks on my computer:
I love how he looks Breadcrumb de Thunar, and now the menus are simpler and more beautiful. The only thing that I could not find is the image for the panel .. Anyway, if you want to give a taste of how things are going, you just have to download this file.