My CX with BB7 discs stops really well; you probably need about half the pressure on the levers that you do with rim brakes, which is a great help when operating the brakes with your hands up on the hoods. In fact I'm so seldom on the drops that 99.9% of my braking is from the hoods.
I really hate using my rim brakes in the wet; all I can think of is my beautiful Ksyrium rims being ground away to a nasty grey paste. It's one major reason why I don't use my roadie in the wet - the roadie is for covering miles at a good average speed in dry weather so the brakes don't get much use except on downhills and the same pads have been on it now for over 4000 miles. The CX on the other hand gets used for family rides, light touring, light offroad, wet weather and winter training so discs are perfect.