For years I rode my acoustic road bike with Shimano SPD road cleats. I found using cleats (aka 'clipless pedals') to be necessary for good power delivery while pedaling at a brisk cadence. Without cleats, your feet tend to fly off the pedals at faster cadences. Plus, you have no ability to pull up on the pedal as you round the 6 o'clock position.
I've tried platform pedals with pins recently on a MTB bike I rented to try out some trail riding. They're not bad at all, and for trail riding I would definitely prefer NOT to be 'cleated-in', just in case I have to get my foot down on the ground quickly.
But back to cleats... about 10 years ago, my knees started to bother me after riding 10 miles or so. This was annoying, to say the least. I did some research and read about Speedplay pedals. Their 'free float' design was purported to exert less stress on the knees, and as an added bonus, made the pedals especially easy to detach from. The old SPD design required that you twist your heel outward against the binding spring pressure that tries to center your foot. But the Speedplay design has no centering spring, so it's very easy to twist out of (but I've never had an unintentional release).
Rather than move to a Speedplay road pedal, I bought MTB shoes (they range the gamut from shoes that look like road-racing shoes to designs that look like robust hiking shoes) and bought compatible Speedplay Frog pedals. My knee pain went away! Plus, I much prefer the MTB design, as the cleats are smaller and located closer to the center of the sole, allowing you to walk perfectly normal... unlike road cleats that force you to waddle with the toes of your shoes an inch off the ground.
Now, some purists will say that MTB pedals don't allow you to apply force to pedals as efficiently as road SPD pedals, but I've never noticed this. I feel I pedal plenty efficiently and can spin fast when I feel like it, and my feet are positively attached to the pedals. Plus, it's very easy to detach in a flash, should the need arise.
So... check out Speedplay Frogs.
