Originally Posted by Andy_K

Nearly any brake can be setup to provide as much braking power as your tire traction allows, especially in off-road situations. It's all about feel and control.

Cantilevers are an interesting brake type because they allow for a huge range of adjustment. The downside of this is that it is possible to set them up with really bad braking performance and can be very hard to get them dialed in just right. Cantilevers can be great brakes once you get them dialed in, and there are definitely reasons to use them. I've got cantilevers on my CX race bike, but part of the reason is that I frequently want less braking power than I'd get with discs.

What I'm saying is that I don't see much benefit in a rear-only disc brake. If you want to go with a canti in front, why not also use one in the rear?