Douglas S.wrote a review of Shimano Dura-Ace ST-R9100 11-Speed STI Shifters on August 6, 2018
Familiarity: I've used it several times
I bought these to replace the D-A 9000 STI shifters. The reason for the replacement the premature fraying/breaking of the rear derailleur cable at its head, at 7,848 miles. I had read that the 9100 shifters extended the durability of the cable.
After installing the 9100 shifters and using them for 750 miles, the shifting on the rear derailleur is not as precise as with the 9000 shifters. The front shifter works well except the force required to shift to the big ring seems harder than with the 9000 shifter.
I will reinstall the 9000 shifters when the rear derailleur cable frays, unless this does not occur until after more than 28,000 miles, the duration of the 7800 series rear derailleur cable.