Check out this edit of onboards shot from the Sauber C30's first day on track. Pay attention at about the 2:50 sec mark you will see clearly, for the first time, how these movable rear wings will work.
I have to say, it looks pretty dramatic but the idea of its FIA regulated use as an artificial passing aid is fairly repugnant to me. As you may know, in the race it will only be available if a driver is following another closely and only in predetermined part of the track! That is such a lame solution.
Anyway, check out the 2011 Sauber C30 in action