I like them just fine on my MTB. I tried them on a mid-level Trek, Domane 3.0 I think, and the extra weight on the wheel made the bike feel sluggish and heavy. Funny how the other trend in roads bikes is lighter & more aero bikes, I guess brakes don't count!

I have Ultegra calipers on my road bike, they work great. On my fixed gears, though, I could sometimes use better braking because I live on a steep hill, and have to ride the brake and back pedal to stay at a safe speed and stop.