I have to use the Wormhole product on my work computers do to one of them being on an isolated network. It works pretty well, but their software isn't as fully featured (and sometimes a little quirky). It'd be nice to have the ID software work over the Wormhole USB cable.
At one point, I did try using a second network card in each computer tied together with a crossover ethernet cable. I think that worked pretty well, but it was a pain to setup and eventually I got a new computer (laptop with a dock) that didn't support a second ethernet port. I suppose there are USB->Ethernet options that I could explore, but the Wormhole cable does about 95% of what I want it to do.