Travellers (not unlike the Vietnamese) seem to fall into 2 camps, those that prefer the North and those that prefer the South. While the entire country is captivating, I found the North to be far more interesting and well worth more than half of the 30-day visa that everyone seems to be travelling on. Hanoi is an incredibly charming city, with SEVERAL day or overnight trips worth doing, while using Hanoi as a base. Trips to Sapa (choose the ones with the Baca Market included), Nim Binh (rent a bike and cruise around the rice paddies) are worth the time, but (AS I WOULD SUGGEST WITH ALL CAFE TOURS) only use the tours for travel and accommodation. Its not at all necessary to stick with the group once you're there. Unfortunately, these group tours are the most affordable way to get to these places though. Just take advantage of them and do your own thing.
Quick Tips:
The train ride from Hue to Danang is among the most beautiful I've taken. Very few tourists actually do it b/c the bus is so easy, but its an incredible way to see the countryside and its only a 3 hour ride or so. Lastly, the Mekong Delta is not to be missed. Inquire with your boat/tour guide about homestays until he finds you someone to stay with. This was an extrememely rare glimpse into daily life in the delta for me, though I only spent one night with a family. Make the extra effort and Vietnam will open up to you. Best Way To Get Around:
Almost all backpackers seem to use the "open-tour" bus to get up and down the coast of Vietnam. While it is BY FAR the easiest and cheapest way to travel, we found other ways to do some of the legs of the trip. If you make it to Dalat (Vietnamese vacation spot, a bit hokey, but nice for some variety), there are tons of motorcycle drivers that will offer to take you around to the sights. The trick is to negotiate a good deal with one of these guys (after spending a day with him first) to take you down the coast a ways for however many days you choose. You will see much more this way and get Vietnamese prices (and a sore butt, but it's worth it). Try to avoid the open tour bus whenever possible. It really turns into a bit of a fraternity party and keeps you a bit distanced from Vietnam.