Throughout our trip to Vietnam, we relied on a great private tour company called Ann Tours. We wanted to see a lot of Vietnam in a fairly brief time frame and they worked hard to get us a custom designed tour including hotels, excursions, guides, and airport transportation.
In particular, Tony, the son of the founder, gave great personalized service. With the miracle of the internet, we would e-mail questions or requests in the evening and have detailed responses when we awoke the next day.
This great attention to detail carried over when we arrived in Vietnam. We were met at the airport for each leg of our trip and had a private van for all our touring with an English-speaking guide. We had three different guides in all and each had a unique perspective on both contemporary and historical Vietnam.
I would definitely recommend a private tour company, and Ann Tours in particular, for anyone wanting to see Vietnam.