The new 9170 Di2 has a number of innovations not seen before most notable synchronized shifting which is a programmable option. You can chose to have the system auto shift the front chain rings based on chain position in the rear or you can program it to shift to the optimal rear cog based on the front chain ring selection.
The junction box is now available in three versions and can be hidden in the frame, handlebar or the traditional under stem mount.
The EW-WU111 wireless transmitter unit, allow connectivity to iOS and Android devices. With use of Shimano's free app and the Shimano power meter it promises to be the ultimate system for any high end road machine.
The new Dura-Ace R9170 Shifters are made for both mechanical rim brake and hydro disc brake with a very similar shape to the current Dura-Ace but a enhanced "mechanical like" feeling shift button. The new 9150 and 9170 Di2 levers have more surface area, more tactile feedback and a louder click on the buttons.