I have the same u-brakes on my cannondale,except they are on top of the seatstays instead of the below the chainstays. I finally got mine working good after reading sheldon browns advice about getting the straddle cable short. I used koolstop red eagle claw pads and now it stops as well as the v-brakes on my wifes trek.

one thing to think of is if the frame is flexing when braking.I seem to remember a "u" shaped brace/stiffener to help prevent this. might also consider salmon kool stops.

despite the bad rep these brakes have I am actually quite happy with mine right now