The movie is great but I also hated it for personal reasons.
I was in Army learning to crawl on my belly while we landed a man on the moon. Our DI was a quiet, yet terrifying guy who didn't need to say much, his cold stare in his eyes did his talking. However, when somebody messed up real bad, he would be called out in front of formation and the First Sergeant was just like Erney in this movie. First time he laid into a person, I started laughing out loud and then it was my turn.
My experience in Vietnam was more like depicted in Apocalypse Now as I belonged to an air cav unit up in the mountains and we went on patrol by helicopter so I found the second half of the movie interesting due to the difference.
Swore I would never return to Vietnam but I did but was armed with knowledge rather than rockets and was amazed at friendliness of the peope including former VC. I ended up making it my 2nd home and this segues into the reason I hated the movie. Living in Vietnam with locals, we are too busy making the most out of each day than to relive the war and I put a lot of bad thughts and memories to rest. A friend who was a VC Commander said to me years ago when we met: "We both did what our government told us to do. The war was a long time ago. Now is the time for peace and understanding."
SPOILER ALERT: This movie unleased bad memories and sadness in the scene where the VC sniper lay mortally wounded on the floor and said "Dau qua, dau qua..." Dau = pain. Qua = a lot. Just when I thought I had bad memories at rest, this movie pulls them back out. But it is better to deal with memories than repress them. Otherwise, they will return even stronger.