Self-reply: It is adjustable in most electric cars at, variously, up to 0.2g or 24 kW of regenerative braking power. This is actually significantly higher than typical engine braking in a gas powered manual transmission vehicle. Engine braking can keep up with low-power, light braking to adjust following distance on highways, and can limit acceleration on a downhill if you downshift to force the motor to run at 3/4k RPMs on a steep hill, and can eventually bring a vehicle to a stop. Regenerative braking can be equivalent to typical braking forces for day-to-day driving, depending on battery capacity and charge level allowing the required power dissipation to be in the range of safe charging rates.

(Note: By "Engine braking" I'm referring to throttle retardation in a typical non-diesel engine, not jake brakes on big diesels. I have no idea how powerful those are.)