From looking online via reviews, the older killer cards were completely awful yet the new 2100 card has received some recent reviews?
I have seen that bit-tech review. Likewise though other reviews say it does make a fraction of a difference:
http://www.overclockersclub.com/reviews/bigfoot_killer_2100/8.htm
Indeed, bit-tech test against a Marvell onboard card, and its not even better in every case!
As for the Overclockers Club:
Card offloads network communication from system - As does a cheap Intel
Increased network performance, especially for UDP traffic - As does a cheap Intel
Plug and play hardware - Guess what, as does a cheap Intel
Application-level prioritization and control - With the included software, which uses more resources than the offloading gains.
The ability to turn off the onboard red LED - Wait.... really???? Maybe I was wrong about this card
Real-time network and system monitoring - Again, with the additional software
Integration with Fraps for FPS control - Can't comment on this.
However, they list NO cons - So they missed out:
Cost
They fact you have to install additional software, nullifying the resources you apparently save.
That the gains you could make are against a onboard card and dont factor in ISP issues such as jitter and losses which is a really issue with the like of Orange.