Other than the usual newbie, come to a stop "oh crap" moment. IT's happened once only, but at favorite cycling venue with lots of hardcore road cyclist to observe. Not a laugh amongst them, just a lot of "it happens to everyone at least once. Don't sweat it." Other than that, the only issue I've had was using shimano cleats with a performance brand spd compatible pedals. Was going down a busy street in downtown Austin coming to a red light I unclipped but the cleat did completely disengage from the pedal. "Oh crap, I'm going to fall down right in front of a line of cars!" Fortunately at the very last moment, as I had tucked my shoulder in to take the fall, the cleat finally let go. Needless to say the cleat pedal combination was rectified that afternoon, never to be repeated.