there is now a new thread, started from an Admin, which in many ways duplicates this one ( this forum starts having lots of duplicates and becomes difficult to follow!)
In answer to @albuzz, I have a 35 and it seems to me that it does hunt a lot less now than it did before, but its performance is far from instantaneous when transitioning from close up to far away range and when operating in low light with whitish subjects showing no or low contrast.
I have a problem with the new firmware. With the 50-140 on, the IS never stops running. I have set it for "Shooting only", but it still runs all the time, as long as the camera is on. What do I do to turn that off? I have mine set up for back button focus, on the AE-L button, and the camera usually set on MF.