If you search diligently (and have an overwhelming thirst for vast numbers of words), you'll see my reporting on Horizonsunlimited.com. That aside, I'll just point out that you're unlikely to ride much of the Ho Chi Minh Trail in Vietnam--it's mostly in Lao. I assume you mean the Ho Chi Minh Highway, which is easily-accessed and far more fun than Route 1.
Poke around the Vietnam Coracle site for more information than you'll know what to do with, but make note of the fact that he tends to gush uniformly about almost any road.
Hope that's helpful.
Mark
