Its just an additional power to the PCI slot. Shamino came up with soldering to the back of the mobo, and adding a 4 pin, but since most people aren't handy with solder on that size pins, I guess EVGA came up with it.
I know I wouldn't call it "clean power" its all the same 12V just probably going through less stuff. Unless there was some sort of capacitance on that mini board its not clean power. If your power supply is garbage, its still going to be garbage. I like the idea though. I would prefer to solder directly to both PCI-E slots that needs the juice. But I am pretty handy with a soldering iron ;)
Rabid - send away. I am still trying to learn how to USE it. Building it was EASY.