Mostly BS as far as I'm concerned. What they describe would be helpful for new games written to use the card, but regardless, I'm quite sure it would not magically decrease the latency on my dial-up connection...
Even if on cable, the card cannot control what happens in between your NIC and mine. For example, if someone on my cable segment has uncapped their modem or done a bad coax tapping job to steal TV I will still suffer horrid latency that this card could do nothing about. There are innumberable other possible sources of lag between gamers PCs. I suspect that this device would see the most benefit on LAN games that are CPU intensive. It probably would be just the thing for high end graphics FPS games on a LAN.