these are some good points.. I recently picked up a BMC commuter with disc brakes.. my first non MTB with disc.. and I absolutely hate the brakes. SRAM elixir setup, brand new bike and the rotors were rubbing on the calipers before I even sat on the bike. I know, apples and oranges - I really am curious to see how a prime example of how road disc setups feel..
Its amazing what we are just on the cusp of ultimate road machinery. Today, it's possible to get a carbon road bike with disc brakes, electronic shifting, full electronic telemetry, and video capture (via Garmin virb) .... the last couple of years have been insane.
The Barfly 2.0 really makes the junction box neat. Best mount out there IMHO.
I have had the pleasure of a few weeks and a few miles on the bike now, and I am even more convinced that this is the future of road bikes.
The lower rotating mass at the rim is noticeable. I know you can achieve this with very light carbon rim brake rims, but at the expense of braking capability. These are mountain bike rims remember (so relatively robust in the grand scheme of things), but weigh significantly less than 280g, so imagine what would be possible if manufacturers turned their attention to road-specific rims without a brake track.
The braking performance is just amazing. With 140mm at the back and 160mm at the front, and the steepness of climbs over here, braking has been consistent, powerful and unaffected by weather. I have had no problem with overheating at all.
I honestly can't see a drawback. The usual responses are:
weight? - the bike is well under 17lbs for a 58cm frame built with standard parts. For somebody my size, that's very respectable, and the ride quality is sublime. I dare say you could get well under 15lbs with a bit of effort (and cash).
wheel changes? - I don't race, so who cares!
danger? - If I crash, the small rotor is the least of my worries. Have you seen what a chainring can do in a crash?! And having lost the top of my thumb in a crash as a result of getting it caught in a wheel with bladed spokes, there is far more danger from both wheels than the rotors.
cost - OK, so here we reach the major stumbling block for most people I fear. At the point of changing over to discs, it means frame, forks, wheels and brakes need to be changed (plus making any spare wheels redundant). It isn't exactly a 'running change' I appreciate, but at the point of changing to a new bike, then it is definitely worth making the move.