I have owned the DI2 on my Orbea Opal and rode it for around 6 months.
Here is what I think.
You really have 0 feedback as far as the shifts go. You hit the button the derailleur moves and you don't really feel it.
You can only shift in one gear increments both up and down the cassette.
Is it smooth? Hell yeah.
Is it worth the money? Hell NO.
Is SRAM RED a better more positive shifting experience? YES
DI2 is great for the cool factor.
The one thing that I will definitly give a big thumbs up for is the front derailleur.
Talk about shifting without thought. Hit the button and it doesn't matter what you are doing and it will shift up without skipping a beat.
For me I am sticking with cables for the time being. Having owned it and sold it I can say that I wasn't overly impressed with it. It's just neat.
After riding RED for several months now I don't think I will change to anything else.
Here is the obligatory picture to prove I had it.
