I'm with Brian, they get in the way. The only time they are worth it is when working down big trunk wood. Then they flip around better then rope.
Right now I have 2 sizes of 16-strand lanyards that I use, 14 ft and 30 ft. The 14 is for every day use where I can position myself for several cuts w/o having to reflip. The 30 ft is used more like a second rope for the big, wide-open spreaders, like American elm.