I've played with it some more and found that it depends on the situation. If I'm on a low-speed road with no other cars around (speed limit 30-40), doing a hard 5th gear accel up to 45-50 and coasting down to 30 seems to work very well. Still not sure it's better than a mild accel... but since it could possibly net more time coasting, maybe.

In normal driving where you can't coast down as much because you're in traffic, a gentle foot and trying to maintain speed without varying so much works better.

Ironically, I sometimes get my best mileage in stop & go traffic as long as I manage it right and don't actually have to come to a stop for more than a few seconds here and there.