Doesn't seem like difference enough to make the ride that much more enjoyable for the money. Also there would be a little gremlin in the back of my mind wondering if the batteries would give out or something very small, specific, and expensive were about to disconnect.
The mechanics of standard shifting are a lot simpler to me, so I find myself more willing to put my trust behind them.
I'd still be willing to put it on a Tri bike for the extra performance, but not an every day thing.

But I recognize that people were probably saying exactly this with the advent of STI shifters, so I won't say my position on it won't changeover time. Also, I've ridden Di2, but never actually owned or spent any significant amount of time on it, so there's a bit of a bias.