I have Dura-Ace Di2 (electronic) on a long-term loaner bike. I've done about 6 rides, or roughly 200 miles on it I'd guess.

To redrhodie: Thanks for your review, I too loved it the moment I started riding it.

To smilingcat: It's not wireless, no issues near any power lines (or anywhere for that matter) on any of my rides.

Buuuut...

While I had the loaner bike with Di2 I didn't ride it for month (travel for work) and the battery went dead. A few rides later I was again off the bike for several weeks and the battery was almost dead.

So, based on this I think, if you ride frequently it could be fine; recharge every couple of weeks or whatever. But on my infrequent riding schedule I felt it had to be recharged every "couple" of rides, which for me made it more hassle than I want.

Hope my experience helps!