I still maintain (as do people who have ever ridden a properly set up cantilever brake) that they stop just as well as any other brake out there, provided you have it set up right. I have never had a cantilever brake that can't be made to stop on a dime, with enough adjustment (well, one, but it was an old Mafac, and I still believe if i had several more years, I could get even that adjusted well).

The fact that they take a lot of effort to adjust is definitely a strike against them, and the fact that so many bikes come stock with brakes that do not work to the best of their capacity only enhances their reputation.

truthfully, I haven't met a half decent brake that can't be made to skid a tire with some coaxing. As I've said, even a crappy Magna brake can do a half decent job, braking power is most often limited by tire traction more than anything else.