I too have a 70-200 F4, it's the IS version and you're right, it's pin sharp.
I also have a 24-70 F4 which is just as good and recently purchased a 16-35 F4 which is probably my new favourite. It's unbelievably sharp with very impressive IS (I was getting pin sharp photos at 16mm while very drunk with an exposure of 2 seconds)
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