I see my spd pedals as a safety feature that I simply would not ride without... the fact that it is the most efficient way to go is a pretty nice bonus!
I prefer the shimano pedals that have the clipless on one side, and a normal pedal on the other side... the shaft is twice the size of the other shimano pedals, and that is important to me because I am a big rider who went through more than my fair share of the other pedals.... plus, if you are ever in a really hairy situation you can flip the pedals and continue to pedal without being attached to the bike!
Mike
__________________
"Ready to retire, just can't afford it yet!"