Originally Posted by
Calsun
It is a subjective decision. For me it adds another point of failure and I have had no problems using standard shifting with the integrated shifter and brake levers that became common 20 years ago. It is one more thing that may fail and I really don't want to start carrying a spare $100 Di2 battery with me on my bikes.
Shimano product managers need a new gimick to sell more stuff as other than bike chains most bike components do not wear out. It also lets bike companies sell a higher level package to price their bikes higher and make more profit. Pro racers will add a new component in part because they are paid to do so, much like basketball shoes on pro atheletes.
On the other hand it removes the widely reported failure point with cables in Shimano brifters. Not that I ever considered that a major problem, but it was always in the back of my mind.
Nobody carries a spare Di2 battery, although I prefer SRAM individual mech batteries. I don’t carry a spare, but you could easily. If one battery fails I’ll just ride with the rear mech only. But not something I’ve had to do yet.