I had tried the 70-200 f4 the non-IS, the IS, also the 2.8 non IS and the IS.
The 2.8 IS is the best of the four.
And then i tried the 70-300 mm IS, and I got stunned. It is as good as the 70-200 f4. As sharp, as good bokeh. What else?
Oh, yes it's got IS which the f4 does not and it's got a longer focal range.
I am amazed at how many people found it less sharp then the L, they either had a bad copy, or were themselves a perfect copy of snobism.
Find a sharp copy and you got yourself an awesome deal, better then the L.