I had aluminum Tektro brakes on my single-speed. They are light, but they are extremely flexy. You had to put in a LOT of force at the lever to get a decent stop. I like my brakes to have some bite -- and these didn't. They were like anti-lock brakes for a bicycle. Panic stops were very long.

I never crashed because of my Tektros, but I came close to hitting a deer and a turkey that I would have easily missed with other brakes. They made me yearn for a set of Shimanos. My next single-speed will have something other than what I had before.