This trip was certainly the highlight of my trip to Vietnam. It was worth the $100 price tag (I opted for the full 12 hour tour - and the price isn't so bad if you can get several people together). The cheap tours cost about $12 a person and are shorter and you are basically shuttled around with limited insight.
Mr. Trung's tour was highly personal. He was an ARVN officer and spent over two years in a Vietnamese prison after the conflict. He is also virtually a prisoner in his country, he and his children are forbidden from leaving. Most importantly, he operates "under the radar". No government operated tour with cue-card lines. No stops every 5 minutes at the latest and greatest tourist souvenir stand. He takes you to the battlefields and gives you a no-nonsense tour.
He picked me up from my hotel, and brought me in a nice comfortable car to the first site, and we proceeded to visit roughly half a dozen sites. It was a rainy day, and the delays caused the trip to be much longer - no problem - I wasn't short changed or overcharged or anything. Along the way, we stopped for lunch.
All I can say is that the tour by far exceeded expectations. I highly recommend Mr. Trung, as he is one of only 2 tour guides I know that can speak excellent English, and can give you a comprehensive tour of the area. He is intricately familiar with the historical context, and with each of the battle sites he takes you to. In fact, to appreciate his tours, I would highly recommend you brush up on your history - at a very minimum read through a few history websites, so that you can come armed with questions, or appreciate the tour.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.