About 30 mins - 1 hour In and it can come in cycles throughout the trip but usually the roughest part for me is the nausea that hits before the trip really starts.
Begs the question...why would you take something that makes you upchuck? I think that it just a minor annoyance. I was sick a couple of times but it wasn't too bad. Once past that it was a beautiful journey. The desert took on a whole new dimension.
The post was old, but I feel your response. It isn't something I hope for or intend to subject myself to any time soon.