This is, BY FAR, the DUMBEST hardware scam in the history of the universe.
Ok, maybe I'm overstating things a tad, but this is definitely hardware for someone with more money than brains.
The overhead of processing network packets with your CPU is less than 1/10th of 1%, and the additional time it takes to have the CPU's instructions travel down the motherboard traces, through the PCI bus, and to the NIC itself is less than 4 ms - I would guess it is actually just 2ms.
Now then.
To spend almost $300 and waste a PCI slot to save that little time and CPU resources to replace a NIC that you already have is just comically insane. There is no way that these trivial improvements will have any real-world benefits to any game. I suspect that anyone who says they see any improvement at all are suffering from a placebo affect, and that if two otherwise identical computers were set up, but one had this card and one didn't, I doubt anyone could determine any difference in any game.
If you're looking to improve the gaming experience, that money is better spent on a surround-sound headphone set, a laser gaming mouse with lots of buttons, a gaming keypad like a Nostromo n52, more ram, a faster CPU, or even a video card that's better than what you have.
When the revolution comes, these guys will be the first that the angry mob sticks in front of the firing squads...
-Llama