I just toured from Hanoi to Kunming in Yunnan. I would recommend my route to anyone considering a tour in Vietnam. Highway 32 cuts through some spectacula mountains and has just been rebuilt so the surface was very good most of the way. Also there was hardly any traffic.
I loved it, Way way way better than the last half of the trip through southern Yunnan which was pretty horrible in comparison.

http://www.crazyguyonabike.com/doc/moving