I have SPD's on my commuter. My only issue with them is they make a creaking sound sometimes where the pedal connects to the cleat.
My road bike came with SPD-SL. I gave them a fair shot but could never get the hang of clipping in. With the SPD's, I just stomp and go. With the SPD-SL's, it was more like fumble around with my foot, think I'm clipped in, push down and have my foot go flying off the pedal because it's actually on the slippery backside.
I switched to speedplay zero's and by the end of my first ride I could just stomp and go. Definitely the best pedal system I've used. I also like that I can have a little float. Feels more natural to me let my feet go how they want to go.