For road bikes I feel that discs are a solution in search of a problem. I'm a big guy and rode in the the Santa Cruz mountains for 30 years and never felt my brakes lacked modulation or stopping power. Occasionally rims overheating could be a concern and I would pull off the road to let them cool. But that was pretty rare. The biggest advantage to discs from my experience is that they don't care what size tire you're running and they're self adjusting. Rim brakes are best up to 28m tires and require much more frequent adjustment for me. I don't like adding complexity to a bike and if I was in the market for a new road bike I would be willing continue going with rim brakes. A cross or mountain bike--yes definitely want discs. The worst brakes I had were cantilevers on a touring and mountain bike--maybe I'm not a good mechanic, but I could never get them tuned so they didn't howl and they provided lousy stopping power.