For those of you who have ridden them, how well do they work? I used the search function, and I only found one really short thread, without too much information. However, someone said in that thread that they are super grippy, but someone else said that they aren't grippy enough for DH. Whoever that was, if you're reading this, could you elaborate, i.e. did your feet slip off, or slide around on the pedals, or what?