The latest Shimano DuraAce is great stuff— I retrofitted the new Shimano DuraAce BR-9000 brakes which are definitely an improvement and allowed me to run a 700 X 27C front tire on my Moots Vamoots RSL.
As for the drivetrain part of the groupo, my main issue is retrofitting all my Lightweight carbon fiber wheels with new hub bodies. This will displace the wheel somewhere between 0.5 and 1.0mm to one side. Clearance looks to be enough, but it is possible that this might make a rear 25C tire too close to one chainstay— I am investigating this scenario soon.
The main attractions for me are as follows:
- 11 speed shifting is a plus, but in particular the new gear ratios which offer tighter spacing on the 11-28 cassette in the big cogs: last two gears are 25-28 instead of 24-28, this is useful while climbing steep stuff.
- Internal seat tube battery (Di2 electronic).
- Slightly lighter weight.
- Although I am tempted by the new 52-36 crankset, I will stick with 50-34 for climbing torque.