Well, its better than Composite, if you only have S-Video and no component, get it, because anything is better. It will help your colors and stuff, not so sure about graphic detail though.
I just got the React S-Video cable from Best Buy and hooked it up. Definitely an improvement over composite - the colors are brighter/better separated, and the picture is a little sharper. If you don't have component ports, and have S-Video, definitely go with that.
