Bottomfeeder

I had the same problem with my cross/commuter bike. It's a Surly Crosscheck frame, Winnwood carbon cross fork and avid canti's. The first time I rode the bike it was so bad I thought I'd never be able to use it. It was worse when I was applying medium pressure on the brakes. (If I applied firm preassure it was rideable.)

I re-checked my pad adjustment (I seem to remember setting a pretty generous 'toe-in' at first), sanded the pads, and after a few days break-in things improved. I eventually switched to V-brakes. Honestly, I don't know why they still make canti's, but I digress. Once in a while the fork will still shudder when I'm just barely dragging the front brake alone. But don't worry. Your bike will be fine.

DanO