I used the 70-200 f/4 L (borrowed) at this concert and wasn't really as happy either. The sharpness is awesome outdoors in good light, but the lack of speed ANDlack of ISreally made shots difficult in that poorly-lit concert. I didn't realize how much I depended on the IS in my 28-135. I think if I'd had even the 70-200 f/4 IS I could have gotten more keepers. The 2.8 IS would have been the ticket, for sure.