When I vas a n00b at clipless, I did have one close call: I forgot to unclip at traffic light (classic) and fell over, partially blocking the lane next to me (they had green light). Fortunately drivers in that lane had time to react and stop instead of driving over my frantically twitching self. Unclipping while laying down proved much more difficult than unclipping when upright.

Since then, no problems. I remember to unclip nowadays. I ride past that intersection every day on my commute, and every time I remember that incident. Practice stopping and unclipping at home before you ride clipless in traffic.

--J