I love EoC and DFCO when I can maintain speed, but then I use extra gas up the next hill. From a purely mathematical point of view, I wish I could coast down any hill that has a significant hill ahead. I used to coast down a canyon in my Prelude, accelerate 55 - 100 solely from gravity, and coast up the other side.
Then I had the crazy idea that was not safe. Now lifted SUVs cut me off going 80 in a 55.
At least for now, I believe that a hypermiler in a gas version of a car can achieve at least equal fuel economy to a normal driver in the hybrid version of the same car.
Should I replace the Prius drivetrain with one from a manual Corolla to find out?
Can you imagine the pitchforks and torches?
"But I get better fuel economy than most Prius drivers!"
"Get a rope!"
Anyway, I have always wanted a Prius for canyon driving, so I would feel less tempted to coast down in an attempt to climb the next hill easier.
When I approach a "6% grade ahead" sign, I coast into neutral as I crest the hill, so I lose some speed, but usually downshift before too long.
Every hill is different, though.