Since I was gone for two weeks and there were quite a few changes in Ubuntu 11.10 during this period, I've made a video with all the new features / improvements:

new Dash design with built-in music lens

new Unity options in CompizConfig Settings Manager such as launcher opacity, mounted devices, etc.

a cool preview feature for multiple windows in the new alt-tab switcher (this might have been there since the new switcher was introduced, but I didn't notice it until now)

revamped Ambiance theme toolbar

a preview of the new GTK3 Ubuntu Software Center (to run it, use "software-center-gtk3")

Among the changes: