I'll admit, I had a front and rear brake when I tried FG for the first time. I was scared of backpedaling, worried about the health of my knee ligaments. That was several years ago, I didn't enjoy myself too much and went back to singlespeed.

This time around I have only a front brake and made a point of having as much control of the FG bike as possible, by applying a bit of back pressure most of the time, while pedaling slowly. So.... now I am using backpressure almost exclusively, to stop. Knees feel fine, to my surprise, though I have not biked down a hill with the FG, yet.