Today I installed campus pedals (mountain SPDs on one side, flat on the other) on my commuter bike. That way I can wear my rigid cycling shoes and my booties (it's getting cold).

Mandatory nod to the thread topic: I don't think I was ever at risk of falling, especially after I loosened up the pedals.

But I don't know how much efficiency I really gained. It sure is nicer to pedal while clipped in (for me), mostly because there is no risk of slipping on a wet pedal or when undergoing a drastic gear change. I also felt that my pedal stroke was better or at least more elegant. It might have been the same with power grip-style pedals, but I've never been comfortable with those devices, which scare me more than clipless pedals.

On my road bike, which transforms power into movement a lot more efficiently, I think that clipless pedals make a huge difference. On my commuter? I'm much less sure.

End of slice of bike commuting life.