I've got disc brakes front & rear.
Setup: Spicer ti frame, 700c wheels, Nashbar steel fork with disk tabs. Shimano XT disk hubs, 36 hole. DT Swiss Alpine III spokes, 3 cross lace. No tying and soldering; I don't think it adds much & the Jobst Brandt book says it adds nothing. Brakes are avid mechanicals (road version) with 203 mm rotors.
My evaluation. It provides plenty of braking power. But the avid mechanicals, as good as they are have some issues which make them a little bit high maintenance.
-The road version still seems to require a lot lever pull and cable travel to activate them.
-If I try to set the pads closer to the rotor so that I don't have so much lever pull to engage the brakes, I find that the rotors brush the pads lightly while I'm riding, and this is annoying. It does this on the front (steel) and on the rear (ti).
-The cable pull problem was such a problem on the rear that I added a travel agent; that seemed to have solved the rubbing issues, and I have good braking power in the rear. But supposedly you don't need or are not supposed to use travel agents with the road version of the Avids.
-I don't have any clearance issues between the frame/fork and the rotors, although it was a little close in the rear with 203 mm.
-finally, disc brakes in general are heavy compared to other options, but you have great braking power and don't have to worry about rim heat or tire blowouts on super long, fast descents with disc braks.