I drove the Auto Road in Sept, 2006. It was absolutely stunning - clear and crisp, just a light haze. I wish I could have enjoyed it more, but I was pretty light-headed and headachy. No chest pains, but it sure seemed odd that I felt so out of sorts. 6300 is not all that high.
Now, i am in generally good health. I drove through the Italian Alps (13500 elevation at the pass) in the late 1980s without any difficulty. Yes, we stopped at the summit to throw snowballs in July and all that. But I ddin't have headaches or shortness of breath or anything like that. A year after that, I was on top of Garmische in Southern Germany, and felt nauseous the entire time.
Have any of you readers felt altitude sickness up on Mt. Washington? I am putting it down to the completely scary drive up the AutoRoad.