I tried these too, and returned them for the same reason Seamus did; they clang and clatter around noisily in the drum. Once they warm up and soften they do get quieter, but that takes about ten minutes, by which time I'm already thoroughly P'd off with the constant racket.
Didn't find the balls left clothing any softer, so still used my usual liquid softener or Bounce as normal, nor did they shorten drying times as promised. Their pummelling action did help to prevent bed linens tangling and balling up (the main reason I tried them), so they weren't completely useless to me. But I since found out that adding a single heavy towel to the load accomplishes the same thing, only with zero noise.
