Ok, so real road racers aside... what about big guys who weigh 220lb and live in areas with huge hills? What about rainy conditions (disc brakes lose a lot less grip in the rain than rim brakes)?

As a bigger guy who's spent quite a bit of time adjusting brakes professionally, I can tell you that there are situations where having disc brakes on a road bike would be nice for me. It's not that I'd die if I didn't have them, but it's nice to always have the range between "a little slower" and "flying through the air sans bike" available, and not have that high end diminish a lot in some situations. Granted, there are situations where the reverse is true (brake fade dragging the brake on long descents), but since I don't ride a paceline, I can scrub speed in bursts. Even in a paceline, I think this worry can be a bit exaggerated (really depends on how crazy long your descents are).

That being said, if you are bigger and want a stronger brake, but don't want as much special design consideration or the wory of brake fade, sram is making some hydro rim brakes (like the old rim-crushers, but prettier). Again, I'm not saying that this is something most people need, but it can be nice to have an over-abundance of braking power if you're a big guy who goes down steep hills.

Sure, they're going to market all of this stuff to people who don't really need it... but there are upsides even for lighter folk. Disc pads need less replacement, less adjustment (on hydro setups), and have an awesome lever feel that makes me smile. The braking surface is replaceable, so the wheel itself will theoretically last longer if you wear through rims (again, fringe problem but I see it happen). Plus, if you decide to do some touring, it could come in handy way loaded down.


NOTE: I only have disc on my cargo bike right now, so I'm not trying to justify a purchase ;-)