On this weekend's ride I did try to get in the habit of calling "downshift" to my stoker when I was about to drop from the big ring to the small. This seemed to help a lot. She could anticipate that the resistance was about to drop and the cadence would spike. In conjunction with this, I tried shifting both the front down & the rear up at the same time. This seemed to help as well. I think that when we dropped from the big ring I would drop one or two gears smaller in the rear.
I also tried to drop from the big ring to the small before I got to big-big. In anticipation of the need for a lower gear, I would drop from the big ring and at the same time try to drop to a smaller cog or two in the rear.
After more experience with Di2, I am beginning to like it more. When I switch from my Dura Ace STI mechanically shifted single to the Di2 tandem, I can see that the Di2 shifts faster. However, I think that our older bar-end shifted tandem shifts as fast & surely as the Di2 - especially on the rear. The Di2 may be a solution for STI but not really "better" than bar-end shifters.
So I may be getting away from the wish for a Di2 triple. However, I'm thinking sychro-shift may be pretty nice for road shifting. Is this just a hope or is it likely in the near future? Is there something inherently more difficult in this than for XTR or have they just not rolled it out yet? Is it possible that this could just be a software upgrade?