http://www.bikeradar.com/gear/catego...upset-12-45511

"Lever throws are very short but significantly longer than Di2"

"There's a bit of a lag while holding down the button before the 'brain' realizes you're asking for multiple gear changes, and while you can move across the entire cluster in just a second-and-a-half according to Campagnolo (and roughly verified by us during our test ride), that's still distinctly slower than what we can do with the company's mechanical drivetrains"

"More worrisome was the handful of times we felt the rear upshift button click but got no gear change in return."

I'll stick with Di2. IMO it is flawless