I have a 2.4ghz router about 8 feet away from the headphone transmitter and hear absolutely no interference in the headphones. The router is directly behind the couch that I sit on to game, so the distance between the actual headphones and the router is maybe 2 feet at most.
I can't comment on whether or not the headphones signal screws up the wireless internet signal, as my xbox is hard wired.
In regards to the sound, I think its great, but again, I have nothing to compare it to. I don't regret my purchase one bit. Hope this info helps.