This stuff is as good as you could imagine.
I currently have two bikes with Di2. Dating back to 2010 when the stuff hit the market. I ride in all conditions and have had nothing go wrong in FOUR years. That includes cross racing. Replace only the chains and keep going.
Di2 can do things you simply cant do with cables. Ride it more than a test ride and you won't go back. It simply never misses a shift. As long as you are at a reasonable cadence ( >40rpm), the chain will not drag or hesitate. Hit the button and it is done!
The biggest reason is often never mentioned. When shifting the rear, the derailleur moves past the cog slightly or over-shifts, after a brief pause it moves back to center over the cog. So when you shift, the chain catches the teeth or ramps of the next gear quicker. Even when under a standing load.
The auto-trim of the Front Der is awesome too. Never hear the chain hitting the fr der cage again. :getsome:
The only thing hindering this movement is price.