I can't imagine how the astronauts felt sitting on top of that behemoth. I don't think I'm exaggerating at all by saying that I would've shit my space-diapers long before the countdown reached zero.
I saw a fascinating talk last week from the guy who heads up the NASA vibration lab. According to him there is so much vibration of your head during launch that its damn difficult to read the gauges much make intelligent choices about what to do next. This was a real concern for the Constellation program which had a lot of vibration issues.
