In terms of being surrounded, surprised and way outnumbered, all of that was true. They made it through the fight in large part due to our helicopter units, artillery and close air suport. Without that, it would have been a massacre.
I know for a fact that the charge on the final morning was fictional. In reality, they were reinforced in the night and cut the final Vietnamese attack to pieces. The charge made for a more dramatic climax, I guess.
Also, Ia Drang really included two fights. The first happened at LZ Xray which was depicted in the film. The second happened when some of the units were moving to LZ Albany for extraction after the fight at XRay. This part of the battle was even bloodier for the U.S (151 killed compared to 79 at LZ Xray) and was not depicted at all in the film.
I liked the movie. I think whatever its inaccuracies are, it probably did capture the experience of what the men went through. Several soldiers involved at Ia Drang (not just Hal Moore & Galloway, who wrote the book) have said as much in interviews.