In iOS 8.4.1, if a caller who has 6 numbers, calls you and you see a missed call. Then, clicking the "i" symbol next to the missed call showed you all the 6 numbers of the caller and the number from which he called, was indicated with blue. This helped in knowing exactly what number he called me from and I could call back on the same number.
iOS 9.0.1 call log does not indicate the number the caller called from with blue (if the caller has more than one number). So, it becomes impossible to call the person back on the same number.
This was one very important feature that made iOS 8 very useful. Apple has taken away a very important feature.