I had one sided SPD pedals on a mountain bike a few years ago - they were a pain in the behind - whatever shoes I was wearing, I ALWAYS got the wrong side, so I changed to full SPD not long after. They're brilliant!

But... I hate having to wear the special shoes for short trips, and they're no fun for walking around a supermarket. So the SPDs stay on my mountain bike, and I bought some toeclips for my hybrid. Which don't fit on the BMX style pedals. I don't think powergrips would work here either, so I may have to buy new pedals. Once you've used clips or clipless, you don't go back to plain platforms.