When it comes to going downhill, it clearly is more efficient to use regen. Letting it coast down in neutral will draw zero power and you get the miles for free. Using regen will feed back some power and you also get the miles for free. Clearly you are better off using regen.
That's a rather incomplete analysis. "Clearly" with the regen you have recovered some energy that you don't if you're coasting. But that energy didn't come from nowhere, it was a result of slowing the car down. So at the end you are going slower. Furthermore, the regenerative brakes are not 100% efficient, which suggests - at first glance, anyway - that it is better to coast!
(It gets complicated because you have to consider the speeds involved. I think it's more efficient to coast down a hill if the speed at the end isn't too large. But I don't have any accurate enough experimental evidence to say one way or the other. I would recommend just leaving the cruise control on and let it adjust the power while the car stays at the same speed. It's probably close to as efficient as you'll get, and it means that you are always going the desired speed regardless of hills. Very easy, very smooth, very simple.)
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Yes it would use a tiny bit of power to make the car stop. It's so little that it's insignificant in terms of energy usage.
I wasn't worried about energy usage, my point was just that it's more complicated.
It's just continuing the concept of driving the car with one pedal, from start to stop, 100% smooth. BMW did it for a reason and is getting great feedback on it. [..]
Fading out regen is, again, just a technical limitation of electric motors. There is no practial advantage to it, there is no good reason. It is trivial to make the electric motor slow down and stop the car perfectly smooth. [..]
Well, I'd disagree that there is "no good reason" - the reason is that that is the natural behaviour. I also disagree that getting this right is "trivial" - I very much doubt that that is an accurate assessment. What exactly does "foot off pedal" mean now? Does it mean "don't apply power" or "apply power in the opposite direction?" How do you handle the transition?
If it is possible to do it well so that the braking power is smooth all the way to zero car speed, then I'd agree with you, it would be a cool feature, perhaps worth the effort to make available. I would worry about lazy drivers not putting their foot on the brake pedal at stops, however. Whether on level ground or not, when stopped the driver should have their foot on the brake pedal (in my opinion).
