Bit fiddly to set up but then they're really decent, very powerful, zero drag, zero stretch, and virtually maintenance free.
Added the quick release mechanism- this will make it only slightly less time consuming to remove the rear wheel!
@Charlie78 the power is nothing short of phenomenal. I can flex the seat stays with ease, with my pinky finger. And there's none of that cable stretch or drag, so it's fast, like bangbangbang. We should really see more of these on single speed MBs.