I recently saw a picture of a climber using something like the petzl String for racking cams to keep the biner from twisting all over on your harness. Just wanted to know if anyone has used them or thoughts. Also would like to know if anybody uses something similar?

The real advantage is that it makes it easier to clip the rope if you are clipping directly to the cam (Indian Creek). The disadvantage is that it makes it more difficult if you want to clip in using an extendable sling. You can still use a shoulder length sling clipped to the biner on the cam, but you probably don't want to use a "tripled" sling. YMMV