Some of the food and nausea comments can easily be explained by fatigue alone, AMS alone, and not oxygen deficiency that is more important at extreme altitude(by definition over 18, 000 ft). AMS symptoms are due to multiple factors such as barometric pressure changes and not strictly oxygen levels. The body must reset its "sensors" and other metabolic mechanisms, taking some time, and is called acclimatization. Steve is correct to say if you are taking Diamox for its (relatively small) benefit, then to start early before symptoms develop. It has it's greatest benefit on the disturbed sleep of altitude but some benefit to daytime performance as well. It is listed as a (PED) performance enhancing drug, but probably only a significant benefit for the subset of people who actually have AMS, not so much for those unaffected.
For all the talk about fitness, food, and hydration just remember that while these are important, a night or two or three( depending on individual) sleeping at say 8k or 9k before Whitney is very important, in fact, many would say it is the single most important factor. Not just opinion, but plenty of experience and studies by others. Yes, there are people who can just show up and "do it" but risk management improves the odds of success. I would value a night of acclimatization over all of the other factors. Yes, I have done HD and W multiple times. AMS is the wild card.
