I had picked up the version II today and started doing some testing immediately. After Canon did such an amazing job of the Mark I 70 - 200 2.8 IS L, I did not think it was possible to get any better. I was wrong. Like the last reviewer, I could not believe how sharp this lense is. It also has tripod sensing for the IS and works more effectively with the 1D Mark IV autofocus. Tried it in EXTREMELY dark conditions 1/6th (1600 ISO, 2.8) of a second and was amazed at the autofocus and the sharp image quality. Great contrast. Excellent lense. Although a little pricey, I am VERY happy with it.