Hi Michal,
With the changes for 12.04, not sure if you have seen the videos, it will be easier for the user to know what the target area of his pointer movement is because the thumb will be reachable at any y coordinate inside the scrollable pane. As mentioned in the other reply, we are also looking into smart friction functionalities to give more precision to the user while operating in the area and ultimately giving him more confidence. The latter unfortunately requires low level engineering work.
Thanks a lot for the feedback and bug reports!
chr