I bought these Shimano SPD pedals PD-M424 http://bike.shimano.com/publish/cont..._mountain.html and have been using them for a while with my Shimano walkable SPD shoes without incident. I recently bought a pair of Keen Commuter II SPD compatible sandals http://www.keenfootwear.com/product/.../commuter%20ii to use with these pedals, and had a big scare when I discovered that I couldn't clip out no matter how hard I twisted either foot. This came as a complete surprise as clipping in was very easy. It seems that the combination of the outer pedal cage, very grippy sandal tread and narrow cleat channel simply would not permit the cleat to release from the pedal. I somehow managed to maneuver over to a parked car and lean against it, and then undid the velcro strap on the sandal so that I could remove my foot. I then rode home with my left foot on top of the sandal. When I got home and got my feet out of the sandals, I couldn't get the sandals off the pedals until I completely unscrewed the tension screws on the pedals. In over 30 years of using clipless pedals, I've never had this experience, even on the track where I set the release tension very high. I tried these sandals on another bike, which has old style SPD pedals w/o the mtb cages, and had no problem releasing, so it seems that problem occurs only with this combination. As to the Keen sandals, they work great both on and off the bike, except like many other SPD walkable shoes, there is some grinding of the metal cleats on hard surfaces.