i may have pulled a few of them, and was not happy, but i only tested the bigger ones and the ones with holes.
they get very slopey and generally are a bit painful, esp the holes: the edge if often very thin and gets into the skin if you push your fingers deep into the hole.
prolly the jibs and the edges are good, but unless they come very cheap id stick to the usual holds, or to edges and stull school-room style!
