I've been running an EWP for a year now - I don't run a controller, the pump runs flat out the whole time. I've moved the thermostat into the top hose of the radiator to keep the pump in the primary cooling circuit.
This setup appears to work without any significant problem even in very high ambient temperatures - I agree with most of what Bob says, I monitor the temp gradient across the engine to check the cooling system performance and typically I'm looking at less than 5 degrees difference - I see two major benefits from the system.
Constant load - there is a constant electrical load on the engine, one less thing to accelerate when you blip the throttle.
Cool down - more importantly I can continue to run the cooling system after the engine is shutdown
I would stay well away from the electronic speed controller setup as there is the potential for significant engine damage - the system was designed and tested on iron block V8's with massive thermal inertia and large internal coolant capacities - the K-series only has an internal coolant capacity of around a liter.