D gives max power and small regen
ECO physically makes it harder to push the accelerator and changes the amount of power for a given pedal position, artificially inducing the driver to not expend as much energy; however, flooring it will give you max power (a good safety feature).
Regen is greater in ECO than in D.
B gives max power and high regen.
Gently pushing the brake (before the hydraulic system engages) gives max regen.
The red needle in the blue zone gives you some idea of what you're regenerating.
See this for the numbers: http://myimiev.com/forum/viewtopic.php?f=10&t=288