How far of a run can you do with S-Video before degredation sets in?

This is really a loaded question. Any cable over say 2' is going to suffer some sort of interference because it's basically a shielded antenna. I'd say you wouldn't be able to notice any degradation at all up to 10' but that's if you're running it in a fairly innocous location. If the cable is going to be running near something with a great deal of EMI then it's going to absorb it pretty easily. These would include an electric junction box in the wall (where the outlet lines are split off of the meter line) and electromagnets like refrigerators, microwaves and stereo receivers. If it's that big a deal, get some of the deluxe monster cable S-video cables.. they're shielded against fallout (j/k) and if you've got the money they've got the length (and I do mean $$).