If you'll all forgive a contrary question:

My perception of "long rail trails" is that they're rather limited. The Katy Trail and the Mickelson Trail, along with the GAP (plus C&O, but that's not really a Rail trail) are trips of about a week of riding. Ditto the Erie Canal Trail. So a longer tour, say 2-4 weeks, is going to have to include quite a bit of road riding. Similarly, the route across Washington state, though mapped, is still 25% roads.

Now I'd expect the Ogre would be a perfectly fine MTB for touring, perhaps better than some MTBs because of the tire width. Forest Service roads should be easily accessible, for instance. I wouldn't mind trying the Great Divide route on an Ogre, except perhaps for the weight, but it'd be a different kind of riding than rail trails.

Am I totally off base?