These products use a spark plug wire with a capacitor.
I read the material on their web site, and remain unconvinced. Their theory is that a brighter spark will produce more power. In my opinion, once you've started the combustion process, it is self propagating. Therefore, you only need sufficient electrical energy to jump the gap on the spark plug. Additional spark energy will only shorten the life of the spark plug.
Since adding additional spark energy is unlikely to result in any additional improvement in combustion, it also follows that it will not result in more horsepower.
Therefore, I don't think you'd gain any real power.
However, they do come in many different colors, so they may look cool under the hood.
I also have a concern about the effect of the capacitor on the dielectric strength of the spark plug wire insulation. It would seem that subjecting the insulation to that capacitive discharge (if I understand the process correctly) would eventually lead to dielectric breakdown of the wire, causing misfiring.
So, based on my short review, and relatively quick analysis - I'd vote no on the Hotwires.