Just noticed today while looking at the sliders example shipped with qt:
the dial has a big circle and a small circle with a trajectory that should be centered around the big circle's center... however, the big circle is not centered vertically (resize window to see that), while the small circle rotates around the vertical center of the widget - so the small circle moves out of the big one.
seen on: qt 4.6.1 kde (oxygen style)
issue was confirmed by a windows7-user on irc