There is already a big hollywood movie coming out about the same exact subject called 300, and this is clearly a rip-off cheapo TV version. I hate it when network TV has to mimic hollywood. remember Tornado (Twister was the real one), Asteroid, (Deep Impact; Armageddon), etc...
The TV program "Last Stand of the 300", produced by The History Channel, is a very cool and interestingly presented documentary and it tells us what really happened at (and around) Thermopylae. The movie "300" (http://www.imdb.com/title/tt0416449/) is not at all an acurate presentation of historic facts, but only the film version of a comic book written by author Frank Miller (http://www.imdb.com/name/nm0588340/).
To name only one example, the movie "300" leaves out the complete story and truly big role of Themistocles who led the athenian navy. He fought the persian navy at sea, in order to prevent, that the persians land behind Leonidas and corner him. Without Themistocles, Leonidas would have failed poorly. The movie "300" has a lot of factual flaws and this documentary helps to know the historic details.
"Last Stand of the 300" by the way seems to make use of a similar look and feel as the movie "300", which makes it very nice as a piece to watch before or after the movie "300" in order to compare facts with fiction.
Another pivotal soldier at the actual Battle of Thermopylae was Dienekes--also absent from the film. He is the one who spoke the famous line "Then we shall fight in the shade," and acknowledged as one of the bravest Spartans at Thermopylae.