Our Di2 is setup with 52/34 rings and an 11 speed 36/11 cassette. I have it setup with synchro shift. We usually ride on the big ring. Synchro helps avoid cross-chaining a lot. The display will beep twice on the shift before it initiates a front shift. This lets me know that before I do the next shift (either up or down) I announce to my stoker "shift". This lets her ease up in anticipation of the shift. A downshift to the smaller ring takes a second or two. The chainring engages the chain before the rear derailleur moves the chain 2 cogs smaller. If we ease up until this completes, all is good. When I forget to announce this shift the torque goes to zero and the stoker is not happy.
I find myself anticipating the terrain ahead and deciding when to move from high range to low or vice-versa. Once we have changed from the high range to the small, I try to stay there for a while. There is quite a bit of overlap between the ranges.
I hoped that Di2 would make me less aware of front shifts. That I could just decide that I wanted a harder (or easier) gear. Instead, it makes me more aware of front shifts (than our old bar-end mechanical shift bike with 3 rings). If a road Di2 setup could be made to work with a front triple, I could pre-program the synchro shift points and likely be less aware of front shifts because they would be less dramatic. We rode the old bike mostly with the big & middle rings saving the small ring as a bail-out. The jump between the big & middle rings on that bike were pretty small (54-44 I recall).