Did some reading up on this technology and it seems to produce some decent power gains. From what ive read it started as race tech and been showing up in production cars/motorcycles in various forms. Toyota, Peugeot, Volvo, BMW, Benz, Porche and that latest Ferrari either have or are in the process of putting it into not only high end cars like the new "La Ferrari" but into regular production cars like the Scion FRS.
There are several different KERS systems that use different parts of the car the brakes/fluid
(HR-KERS), flywheel
(F1-KERS), CVT transmissions + differential
(CPC-KERS) and battery with electric motors
(HY-KERS) are the most common. But the tech can be applied to almost any moving part on a vehicle such as the engine (like a supercharger does) and even fluid systems ie shocks and coolant.
So would you trade you turbo or supercharger for a small Volt like battery with a KERS system if the weight addition was a little more you got better MPG and a 140 hp bump vice a 180 hp bump.
And for the haters of anything "hybrid" a traditional supercharger could be added for more
Gen V LT(X) engine plus a KERS system and an 8 speed transmission in the ZR1? any buyers?