I have the HM quick shifter, the stand alone system & its the mutts nuts
Another point to make in the stand alone HM's systems favour is that it cuts the ignition spark, not the fuel.
The Power Commander version cuts the fuel, this can cause errors in the ECU. Cutting the ignition spark, as opposed to the fuel, is thought to be kinder on the engine and create a cleaner ignition cut, therefore its easier on gearbox components as there's no chance whatsoever of a power cycle.