This cord is in my opinion the best value in photography. While most people use these with flash brackets I think that the real utility of this cable is using it to hold the flash in your left hand and bounce the flash off of walls, ceilings and objects, making quick lighting adjustments easy on the fly.
Using this technique you can get much more sophisticated lighting effects than would be possible with the flash on the camera and you can do it very quickly. It is just the thing for wedding and party photography or fast paced portraiture.
The SC-17 gets the flash off of the camera and maintains full TTL integration with both film and digital cameras.