Now that I've seen the movie, I have a one line review: the only things missing are the Nazi arm-bands.
Seriously, this a movie about how wonderful and beautiful and spiritually rewarding it is to die in warfare. We don't know whether it's good to die for a cause, because Sparta wasn't really a "cause"-- just a repository of mindless war and oppression.
In real life, the Persians were rather enlightened and well-regarded as far as empires go. They gave Jerusalem back to the Jews and ordered the Babylonians to return all the sacred relics to them.
In real life, Athens was worth fighting for: the prize of culture and learning and philosophy in the Greek world. Can you think of any Spartan philosophers, play-writes, or kings, other than Leonidas?
And it was the Athenians that inflicted the more significant wound on the Persian Empire with their naval victory at Salamis.
Oh, by the way, of course, the Spartans actually had an army of 5,000 other Greeks with them at Thermopylae. Didn't notice them in the film, did you? There is a core of truth, in that 300 Spartans were a particularly effective force within the over-all effort-- oh, what the heck, let's just go crazy.
Before anyone rushes off to worship at the alter of "300" and rhapsodize about the beautiful, fit Spartans and how courageous they were to give their lives for freedom and liberty and their lovely, sexy wives, it ought to be remembered that Sparta was to freedom and beauty and life what Reverend Jim Jones was to true religion. The Spartans hated freedom, as much as they hated Athens, which did stand for freedom. Every soul in Sparta was expected to sacrifice his or her personal interests for the military good of the state, to the point of death.
If a soldier fled the battle scene, every soldier in his group would be executed for cowardice.
Yes, yes, let us duly note that compared to modern times, the notion of "freedom" in Athens in 400 BC was relatively constrained.
When babies were born, they were tested for toughness and strength. If they failed the test, they would be abandoned on the side of Mount Taygetos.
Young boys were sent for military training by the time they were seven, at which time they might also enjoy the privilege of serving as the object of sexual gratification of an adult male.
It wasn't all bad. Women in Sparta had many rights, including the right to hold property, and to go where-ever they pleased. Divorce laws were the same for women as for men. It seems that Spartan women were allowed to bring lovers into the house if they pleased, and to bear the children for other men-- for the benefit of the entire commune. They dressed in short skirts, while the Athenian women wore bulky, long dresses and robes. This was remarkable for it's day.
Sparta's women were also educated, and they took part in athletic competitions, and there are accounts of Spartan princesses leading troupes into battle. Really, it's kind of extraordinary. Why doesn't someone make a good movie about this?
Sometimes these women would hold a contest to see who could take the most severe flogging. I am not making this up. More movie material.
So the primary benefit of the courage and fortitude of the Spartans is that they help preserve Athens from the potential ravages of the Persians.
In terms of Spartan art and culture, relics are conspicuously absent. It appears that it just didn't exist. If you could picture an entire society that operates and functions like an American college football team, complete with token curriculum and cheerleaders, you have Sparta.