I ride clipless only, all the time. SPD/mtn. My wife has clipless only on her road bike, and dual-sided on her mtb. I tried her pedals out, and was constantly frustrated getting the pedals flipped over to the correct side.

For me, if I ride platforms, I'm forever shifting my feet around trying to figure out what's the "right" place to put them. Like the old man with the long beard, when somebody asked him whether he slept with his beard under or over his blanket and he never got a good night's sleep again trying to figure out which way felt "right"!

My spd shoes are traily/hikey enough looking/feeling that I don't mind wearing them around. They are perfectly fine inside stores on carpet or linoleum, our outside on dirt or grass. The only annoyance is outside, the cleat scraping on asphalt. Once in a great while, I'll ride a short distance on the spd pedals in just tennis shoes. If I really need different shoes at my destination, I can throw them in my bucket and ride clipped in.