tested with VDub 1.7.8. The new AQ shaves 9MB off a formerly 54MB video. CQ 4, little over 3mins. This is Gears of War footage.
I couldn't tell a difference playing at full speed. Frame-by-frame, no AQ was better overall, but only very slightly. Some frames it actually seemed to help.
One thing I did notice was in the beginning, I had some text that was in a special font. It was a deep red, with small black holes in the letters. Just interesting.
No AQ:
AQ:
It's a lot easier to see a difference flipping between them