The Ultegra Di2 series with electronic shifting is "pro-proven" as it is a direct trickle down from the Dura Ace group. It stands for state-of-the-art technology, proven in pro races, the technologies used in the new Ultegra 6870 series 11 speed, newly designed brakes, new chain treatment etc. The electronic shifting lets you concentrate on your performance.
All the benefits of Ultegra but with the excitement of electronic shifting. That means there are a few more components and options, such as frame or seatpost-mounted batteries and remote gear shift buttons designed specifically for triathletes or sprinters. The beauty of electronic gears is that the derailleurs self-feather, giving perfect, quick shifting every time. They make a rather satisfying little ‘zip’ noise when they move, too. And that’s not the only exciting thing about Ultegra Di2: you can also specify Ultegra Dual Control STI levers which come with a hydraulic capability, meaning Ultegra Di2 hydraulic disc brakes are available, too.