Still hasn't all of this been tested with MTBing? I have rim brakes and with all of the spare wheels I have it is hard to justify getting a road bike with disks. However my MTB sure seems to work better than my rim brakes did on my old MTB.

The only real question would seem to be are disks necessary on a road racing bike and do they pose a risk to other riders? Why one has to ask are they safe for Cycle cross and MTB racing. As far as weight goes there is no reason a bike can't make weight with disks considering some have to add weight now to make the minimum.

In the dirt they do work better. When my brakes have been wet the Disks work better, it seems to me anyway. Should racers use them? I don't know that would be up to the teams and riders but I am not sure mixing brake types are a good idea.