Alot of your expensive ethernet cards have had this technology for years now.
Something like this is nice if you're working in a datacentre environment, but as far as it being useful on a desktop? You're not going to see any significant performance gain from purchasing something like this. That company is exaggerating the usefulness of such a thing; it isn't going to help you any unless you're doing alot of I/O operations over the net (much larger than any game would need), but it is convenient in that it does remove unnecessary strain from your system's CPU, just not enough to notice unless your box happens to be a server that's serving alot of information.