I love my Ultegra 6770 Di2 which came on my bike when I bought it November of 2013. I have only charged the battery 3 times in 15 months. You can tell when it's time to charge because the rear shifting will begin to feel slightly delayed but usually even after you notice it, you can squeak out another week or two. It doesn't just go dead in the middle of nowhere. Charging takes about 30 minutes and unless you ride all day every day I can't see how that's an issue? You can also mix and match the components like using the less expensive Ultegra 6770 10 speed shifters with current Dura Ace or Ultegra 11 speed derailleurs or vice versa by simply updating the software. (The 1st generation Dura Ace 7970 Di2 is not compatible with any other system). What really sets it apart from mechanical is the amount of lever throw, with Di2 its just like a mouse click, no effort at all. Plus, the hoods are much more compact which to me just feels and looks better.