It's interesting how reminiscent that design is of Google Wave's much-criticized scrollbars: the position indicator following the thumb, the page-up/page-down buttons, and the minimalist appearance when not in use. I wonder if Wave's design was just ahead of its time.

I think that the problem with Wave's scrollbars wasn't so much that they were bad, they were non-standard. Scrollbars are OS territory, individual webapps should probably not try to reinvent them. (I would argue that they should only ever try to reinvent them when they provide something substantially better and when the standard OS implementation is lacking.)

My problem with wave’s scrollbars was that whatever code they had to do scrolling was dramatically slower and glitchier than native scrollbars.

I think the problem most people had with Wave's scrollbars is that they didn't indicate the height/length of the document very well. The Canonical design above has solved this by retaining the visual indicator.

And OS X Lion's new "hidden" scrollbars.