Cheers all. We're getting on pretty well together
The CR720s are pretty good. A definite improvement over the BR550s I used on my last Surly. I'm not sure how well I've set them up but they stop me and modulate pretty well.
They do take a bit of force to bring me to a stop when travelling at a fair wack - no way near as much bite as my road bike calipers.
But like I said, that could be my set up, and they would no doubt be improved with some decent pads.
I would definitely recommend them over the other cantilevers I've used but can't really give an accurate review as I have little experience with this type of brake.