I switched to SPD a few weeks ago. No problems, however, at one time a car gave way to me just after I had come to a full stop with my right foot on the ground. I wanted to clip in quickly and while in motion, I pushed my right foot downwards; and it didn't clip in but slided forwards off the pedal. Luckily, I was sitting, but still it hurt my groin, because of the sudden position shift. Youch! Must have been a funny sight for the driver, who thought to be kind, by giving way without a real reason.