How are the newly discovered Janus/Epimetheus rings different from the other rings of Saturn?
http://saturn.jpl.nasa.gov/science/moons/epimetheus/

Scientists believe the ring formation was due to the break up of one moon. Cassini has taken photographs of the moons and Voyager was the satellite to allow scientists to discover the moons and the rings which follow their orbit. What is seemingly special about these rings is the structure. 

http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=2277