NOTE: Animations are way smoother in reality than in the video, of course.
New subtle animations and timeouts just hit the development version of overlay scrollbars for ubuntu 12.04.
The tail (visual connection between the thumb and the indicator bar) now retracts when the thumb is hidden.
The "jump to" using the middle click features a smooth animated scrolling.
To further reduce visual clutter (floating thumbs appearing too often), a smart timeout waits before showing the thumb, but when it's close to the screen edge, it respects Fitts' law and is immediately revealed.
Opinions? a PPA is available for Oneiric users.