I have a C59. Personally...I don't get the "race to the bottom". The ride quality is only good up to a certain point.My frame comes in @ 14 lbs 14oz. My training weight fluctuates between 174-180 lbs. This frame gets stressed pretty heavily with Mondo gearing.
I think that in real world conditions as an everyday rider, with chip seal road surfaces and high winds, you are pushing the limits of the bike. At high speed, everyone of these frames start to exhibit their flaws i.e. a lack of stiffness. I cannot imagine how anyone would want a bike in the 12-13 lbs. range ... it would be trashed in 10-14 thousand miles with excessive hammering and the ride quality going down from there as you descend the big mountains daily. Why pay a premium for that unless you just want bragging rights and have everyone at the shop pick it up and go...WOW! I wish I had THAT!
I know ... you can climb faster and spin up to speed with ease. But in the end ... ?
One pound on a bike is not going to make a material difference. One pound is the weight of a filled water bottle. Ask yourself if you ride any faster with or without a filled bottle. There are a great deal more important factors in a road bike. If the frame is too stiff and your body takes all the impact of the ride and tires you out at the end of a long bike ride, then that is going to matter far more than 16 ounces. Add to that stability or how well the wheels stay planted. I ride a c-59 and the thing that I love about it, is you instantly feel that you and not the bike are the limiting factor and any training and improvements you make in your legs and endurance will be rewarded. In the one year since I've owned my c-59 my speed on long rides 50-100 miles has improved by 2.5 miles per hour, and that's with significant climbs.
Agree that Colnago intentionally makes the c-59 a little heavier, in order to make it durable. Make a 700 gram frame and something's going to have to give, be it stiffness, durability or comfort.