I thought the movie was well done, and from what I've studied of Mayan history and culture, didn't go over the top in respect to gore and violence. Quite the opposite if the interpretations of glyphs left behind are accurate.
There was one historical error, that most people probably didn't realize.
The Mayan culture was very advanced for the times, but as it grew and the cities consolidated, the social strains proved to be too much to contain. Power was shifted throughout the region many times, each time resulting in groups of peoples with no ties being moved to the new seat of power. In-fighting between military groups and their families would escalte usually at the expense of the common worker. The priests in order to restore order, and retain their positions of power, intensified worship and sacrifice as a way to shift attention away from social evils. It apeased the masses for a while, but eventually failed to mantain order. The culture started to spiral out of control, and a disorganized series of civil wars broke out with no clear winners, sealing the fate of the larger cities and those who ruled them. Basically their society broke down. Many of the large cities and cultural centers were stripped for building material. The religion did continue as much of what was taught was telling of the future. The empire was shattered, but functioning at a grass roots level, and the people were left waiting for predictions they had been taught to unfold.
Interestingly enough, one of the predictions was of large white-winged canoes carrying hairy faced men which would arrive from the east. They would shine in the sun, and were there as represetatives of a group of Gods. They were to care for and lead the people. This prediction was made between 400 and 500 years before the cities and temples crashed. The first Spanish ships arrived nearly 400 years after the collapse. There were no major Mayan cities or religious centers that were still influental at the time of the Spanish arrival despite what the last scenes in the movie showed.
The majority of Mayans, when encountering the Spanish for the first time, defered to them as servants. The Spanish, with the blessing of the Catholic Church, conquered them easily with very little Spanish blood being spent. (Mayans not so lucky)