Hanoi is wonderful, full of old Viet charm, wasn't overly impressed with HCMC, but good war museum. Hue is on my list. Hanoi is cheap as chips (that and Hoi An are my fave places)
Things to avoid.........Waiting for an opportunity to cross the road in HCMC, you will never see so many mopeds in your life, an experience in itself. Enjoy, I did !!