I just got back from a South East Asia trip including Vietnam. Unfortunately, due to the finicky weather this time of year, I didn't get a chance to make it north to Hanoi and Halong bay. The south was still incredibly pleasant and I would highly recommend it. Did you get a chance to check out Hoi Ann on your trip? It was by far my favorite city in Vietnam of the ones I was lucky enough to visit. Great post btw : )