At the hounding of a cycling friend, I caved. I bought Avid BB7 disc brakes for front and back. I have replaced rubber brake pads before, but I have never installed new brakes and I have never installed disc brakes. It presented a certain level of anxiety as you have to align the whirling disc inside of the brake, without it hitting as it goes flying by. This certainly cant be easy.
But in fact it was. It's a bit hard to describe: first you get the wheel relatively in line, which should make the disc relatively in line. Then you squeeze the brake so that it clamps onto the disc, and tighten the brake bolts so that the brake lines up with the disc. After this, there are some adjusters to make minor fine adjustments. It didn't take long before I could adjust the brakes on the fly as needed.
Disc brakes offer clear advantages over V brakes. First there is the "not wearing out your expensive wheel's rims" thing. The disc brakes give me better feel; there is a greater difference between lightly applying the brakes and a full squeeze emergency stop. In addition, disc brakes are less affected by water, dirt, and mud ~ all those wonderful conditions that come with off-road cycling and which will chew up a rim if you use V brakes.
Disc brakes started on mountain bikes. They have moved into the Cross Bike category and you are now even seeing them show up on road bikes (even though they do add extra weight).
So what's the take away? After several months of riding with discs, I love the responsiveness and I love the fact that I am no longer destroying my rims or replacing my pads near as often.