I don't think it's about their being a French product, it's not for me and it shouldn't be for the rest of us: these are inanimate objects, they don't have any "personality" unless we give them that quality. But looking at just the cold facts, Mafacs have about the same stopping power as the aluminum centerpull competition from the same time period (Weinmann, DiaCompe copies of same, Universal), which is to say not very good compared to the state of the art today. But that's an unfair comparison. Most vintage CPs can be decent performing brakes when they are clean and lubed, set up with good cables and (most important) good pads (like KoolStops). The unique down side to Mafacs (which some people consider a plus) is the way the unthreaded pad and Mafacs attachment design allow for another angle of the pads to be adjusted (and got wrong, too). I think it's this feature that causes many people to set up the brakepads with poor rim contact and the result is the squealing that Mafac Racers are infamous for.