I drove a MINI E for a year, and the term we used for that was "feathering" the pedal - that's how i've been doing it on standard regen, and i've a nice 1/2 mile downhill on I-287 that yields a lovely and long green track on my energy graph. But i'm interested to see if i put it on low, if i can actually produce a deeper regen for longer with the added momentum.
I have not tested this out yet, but plan to do so this weekend. Low regen obviously gives less regen than Standard, but still gives (what appears to be) way more regen than I was getting downhill with cruise control set. Plus it would slow you down much less than Standard, effectively letting you coast downhill. I also notice that you can play with this a bit by letting off the accelerator (but not entirely) when going downhill, even with Standard on. I think it will just take some practice to see what works best. I'll try to post some numbers for how much regen I see in various scenarios on the same hill.
If you're trying to maximize range, you do not want as much regen as possible:
1. Mechanical brakes are super evil - avoid completely whenever possible. Regard them purely as an emergency safety mechanism.
2. Regen is evil - you waste energy by using the motor to build speed, and you again waste energy by using the motor to reduce it. Electrical losses are somewhere around 15 to 30 %. But in addition to this, tire resistance increases dramatically when you accelerate or decelerate, because the rubber slides against the road surface, and it deforms much more too. I don't know how much this is, but I think it would be hard in practice to regenerate more than half the energy you spent, considering rolling resistance and electrical losses both ways (out of and then back into the battery).
3. If you have to brake, use regen, but do it early so you can regenerate at as low power as possible.
4. Using more power (in the physics sense, measured in watts) than necessary is bad. This is because both electrical losses and rolling resistance increase dramatically with increasing power. So to conserve energy, you want to accelerate and decelerate relatively slowly and maintain an even power consumption. Note that this is very different from maintaining an even speed. Accelerate and decelerate as though you were transporting your daughter's wedding cake unprotected in the passenger seat.
In hilly terrain, imagine that you're a rollercoaster. This is the ideal, a rollercoaster does not waste any power maintaining speed uphill, and then regenerating (or - heaven forbid - braking) downhill. Even if you avoid regenerating downhill, you will waste energy unless you simply coast over the top. On a public road, this is obviously unachievable, but it helps to know what the ideal is.
So if you're approaching a smallish hill and there's no one behind you, try to estimate early on how much power you have to apply to clear the top at your minimum acceptable speed. Then feather the accelerator so that gravity decelerates you at the rate that will let you reach the top at that speed. Then you either coast back up to speed down the other side or just keep applying the same power as during the climb to accelerate back up to cruising speed if the road is level. This minimizes the power and therefore the losses.
Turning also increases rolling resistance, so it helps to drive the racing line as much as safely possible. It's better to take the corner at higher speed if that can be done safely rather than regenerating first and then accelerating again. Hoard your kinetic energy.
Now don't take this too far, or other drivers will get seriously annoyed. Just knowing how it works helps, there is usually some wiggle room.
There are also some tradeoffs that complicate the picture if you really try hard to conserve energy. For example, accelerating a bit before you enter an uphill will get you to the top in a shorter time and reduce the required power, but this will also increase air resistance. It's hard to say where the optimum is without detailed and unobtainable data.
I don't often drive like this, but I can squeeze out quite a bit more range than usual if I have to without being (too much of a) nuisance to other drivers.