<---rank beginner MTB here and I use the double sided Shimano SPDs on my MTB. One side is clipless, the other side is flat with a cute little spot for my cleat to fit. I Love them on my MTB coz when I'm cruising along feeling very good and comfortable, I can be clipped in. If I see something coming that looks scary to me, I can unclip, flip the pedal over and ride on the flats (coz I promise you I'll fall!)
currently my falls to rides ratio is 2:1!
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"