Originally Posted by CdCf
Actually, I really disagree with you there.
On a road bike, wheels are typically fairly expensive and you want the rims to last as long as possible. Using rim brakes isn't very helpul in that situation. +1 for discs.
Road bikes see rain and dirty roads/streets too. Rim brakes do lose braking power in wet and dirty conditions. Disc brakes are far from the road surface and are less susceptible anyway. +1 for discs.
Disc brakes makes the bike somewhat independent of wheel size, as long as they're fairly close to "normal" size. This could allow road bikes with narrow forks to run wider tyres on 559 mm rims, since the fork usually widens closer to the hub. Sure, this isn't something people are screaming for, but it still opens up the possibility. +1 for discs.
The added weight is not that great, even if it is more than negligible. For an Avid BB7, it adds about 150-200 g or so, when the weight of a normal front brake has been deducted. If wheels are made lighter as a consequence (no extra rim material to wear down), some of that weight will have to be deducted as well. -1 for discs.
Discs are slightly less aero, I would think. Not much, but a little. -1 for discs.
Road wheels don't usually cake up with mud though- whatever dirt gets on there usually gets cleaned up after 1 rev. Braking with wheels caked in mud is a big plus for disks on MTBs
Road wheels are higher pressure so you can't make the rims too thin to save weight.
200g can be a 25% weight penalty for a front wheel, maybe not a huge deal but hard to sell to a weight weenie.
Disks require a more severe dish to the wheel.
I'm not anti-disk... I just don't think they've got enough advantages to make it worth while.