Days ago, Ubuntu 11.10 shifted from GTK+2's Ambiance and Radiance to GTK+3.
Although this process was mainly about porting the light themes, there are some minor extra "stuff" from an UI point-of-view:
- tolltips have prominent borders now


- menu entries have "highlighting" lines (directs the user directly to its particular task, separates various actions such as "redo" from "cut", etc, so a "+" in usability)

