[ghaff]

>(and most of the rest of the country outside the NW corridor)

I assume you meant NE corridor although I understand that Seattle to Portland by train works reasonably well. Even on the NE corridor it's really segments. Boston-NYC and NYC-Washington DC work well. Boston to DC really takes too long although I've done it.

There are some other segments here and there but even when they seem like a good way to get from A to B (like Raleigh to Charlotte), in my experience it's not heavily utilized.