I don't have it myself, but if I had the money I'd probably go for it. One of the advantages I can see is that you don't have to think about which chainring you're in, and it can be programmed to jump several steps at on the rear derailleur when you change the front one. That's obviously for a 2x setup. Having just got a mountain bike with a 1 x 12 setup, I actually found myself thinking the other day that the gear change was so slick that I couldn't see electronic shifting making a whole lot of difference.
I do find myself having to fiddle with the barrel adjuster on my road bike when the weather gets really cold; I presume the cable must shrink fractionally. Maybe I should spend more money on cables? Anyway, I guess you wouldn't have to do that with Di2 or Etap. That's a lot of money for a marginal gain, though.