Everything I have read either concludes "no measurable benefit" or "statistically significant, but not clinically significant benefit; need more research". That latter is hard to distinguish from noise. What have you found that concludes otherwise?
Irrespective of the common cold, vitamin C is uniquely beneficial in many different scenarios. Negative paper on vitamin C is almost non existent.
Speaking about the vitamin C and common cold, since you don't have any good papers in mainstream medicine that tested Pauling protocol you must turn to those groups that did so and use it in every day practice - orthomolecular practitioners. I am sure you will recognize this is considered frindge science by mainstream medicine but that is irrelevant since they didn't do the job. The situation is similar to that of vitamin C and cancer. Original claims by Pauling were not tested and instead we got Moertel studies on Mayo clinic that concluded that Pauling protocol does not good, except that they didn't test it at all. Check out the history here, highly informative paper:
Most of the experiments were done by Dr. Cathcart who treated over 20000 patients using vitamin C and extensively documented it. Book "Ascorbate, the science of vitamin C" by Hickey is also very informative.
But don't limit yourself to common cold, just look everything that vitamin C does in the body, and I am sure you will change your opinion.
The fact is, AA is the main anti-stress molecule for the animal body (thats why they didn't delegate production to plants and still produce high quantity of AA from glucose on daily basis), just as GSH is primary endogenous antioxidant and detoxication agent.
Humans did have some adaptation to GULO loss for sure, but modern lifestyle sure as hell topped that in other direction.
The major problem is dosing as half life of vitamin C is very low and you have to make the dose right in order to neutralize it or effects are not impressive. See this graph by Cathart:
which says that symptoms start to disappear only when you are very close to bowel tolerance. Notice the dose also - 1g per day is non existent compared to ~100g per day that Cathart used. I tried that many times, and it works for me. It is especially true for alcohol intoxication where the same protocol will bring you back from nonoperational to fully normal person in few hours.
