A couple of thoughts to share, and possible discussion topics...
I think all hybrids right now blend regen into the brake pedal operation, which makes sense from a traditional driver's point of view. However, I know a lot of you like to drive the Volt in L mode, where regen is also blended into the gas pedal, with strong (full?) regen when the foot is completely off the gas.
I think started thinking about a recent Tesla report that said the Model S will have an option to reduce the regen and provide more of a coasting effect that is preferred by some drivers, but that it would hurt range slightly. That is when it hit me. I think maybe Tesla is not blending regen into the brake operation, and that it is only tied to the gas pedal operation.
I am now starting to feel that the gas pedal only blending (which I suggested that Tesla might be doing) is actually a better design. It would be far simpler to implement, with no real drawback to the driver (with one exception I'll note at the end). With regen only tied to the gas, the brakes can remain as simple hydraulic brakes like on any ICE car. Meanwhile, blending regen in the gas I would think should be quite easy (much more so than trying to blend into brake).
The only drawback is the issue of the brake lights not coming on when regen is active. But that seems like it would also be pretty easy to fix -- just make the brake lights come on when the brakes are pressed OR when the regen exceeds some threshold.