I like the idea of an ICE off button to gain a little extra efficiency especially in the situations TimK states, downhill, approaching stops, etc. It could be designed like the Cancel button works on the cruise control. Older Fords didn't have the cancel button you had to tap your brakes to turnoff cruise. I hate doing that since it sends a signal to approaching cars that you hit your brakes. The Cancel on cruise lets you coast to a stop without having your brake light come on. So why not an ICE off button. Of course the computer would override this in situations where it could not occur, low SOC, during warmup, etc. but in situations where all systems were okay shutting off the ICE could gain some MPG.