Thanks for everybody comments. I think the general feeling is that gear ratios are significantly more important than frame geometry when it comes to trailer touring, especially in the hills and mountains. Perhaps I will find a nice cyclocross frame and set it up with a triple.

I have considered using my mountain bike for road touring, and I do occasionally put slicks on it for the road, but even with bar ends, it just doesn't seem like it would as comfortable or fast for long multi day road trips. I dream of some day riding the continental divide trail with my mountain bike, but alas, that requires more time and money than a poor grad student has ;-(