Cyccommute, you're right that I would want suspension for bombing a steep downhill full of babyhead sized rocks and deep channels at 30mph. Most people I've met don't do that even when out mountain biking, though we don't really have any long straights like that around here. It's all widing through the woods. From what I'm picturing, I would still use a ridged bike for that type road if touring. I just wouldn't bomb those hills at that speed. I think what you did is pretty abnormal for touring, though, and based on OPs post, I have a feeling he won't be doing anything nearly that extreme.

And for what it's worth, I wasn't talking about WI rail trails before. No way I'd even use a mountain bike for the ones around here. I've ridden my 25mm tire road bike on some of those before and been just fine. 38mm touring tires are perfect for such terrain.