What got me to switch to clipless for good was commuting in a sharrow on the outer lane of a very busy road (2-3 lanes each way) with people trying to share that lane with me as I went down a hill at 40+ mph and my foot slipped off the pedal. Tight quarters, high (to me at the time) speed, on a road with questionable pavement, and I was looking down trying to find my pedal and thinking, I've got to find a way to get more locked in. So, it wasn't a climb that convinced me, it was a descent.