Bought this Lense finally two weeks ago. Taken several test shots of grids and patterns. Its like xerox copier. Accurate as heck!
This is it. The Lense.
With 20D body,it dont lose target easily, but that happens occasionally. I have photographed airplanes on air, which at a times is challenging for camera/holder ;o)
Weight and size is con of this Lense, but it seems to be best money can buy. More morning porridge will compensate the weight.
For others, theres sad news: Manufacturing this Lense has been stopped.