After shooting the F4 non-IS for awhile, I noticed from my shots that I needed the extra stop and IS. So I finally received my 70-200 2.8IS today. After reading all the topics lately regarding the softness of the 2.8 version and seeing differing MTF charts, I wasn't sure what I was getting. I was initially hesitant since my F4 was very sharp and feared the 2.8 wouldn't deliver.
I did some initial testing before I head out to Carlsbad flower fields this weekend for its true test. Below is a test between my F4 non-IS and F2.8IS.
70-200 2.8IS (70mm, F2.8 )
70-200 2.8IS (70mm, F4.0)
70-200 F4 non-IS (70mm, F4.0)
As you can see, hard to see the difference. For the pixel peepers like myself, I have attached the links so you can see the original file.