I've considered using them, but what put me off was that if I'm going to be casting a good distance I prefer to use a single flapper rig with a penel hook setup and silicon stoppers so the swivel slides to bottom on hooking a decent fish anyway effectively lifting the lead clear like a pulley does.
If I'm fishing rough stuff then a pulley rig but I don't tend to chuck too far when fishing rough so the features of these things are redundant for me at least as a normal decent sized swivel does the job.