When I saw the first trailer, I thought "This is Gladiator-lite with some SFX from a PS2!" But I have to admit it does look good with the extended trailer.
Frank Miller wrote the the series of comic books (or are they Graphic novels?) that the movie is based on. He is also the author of the Sin City series:http://moebiusgraphics.com/comics/300.php
The movie is based on his story for 300 rather than the strict historical evidence that is know regarding the Battle of Thermopylae. For instance, not all of the Greek force were Spartans according to historians. So this movie is more about the Frank Millers work than history. Not that there is anything wrong with that.
Without wanting to sound like a geek, you guys should read up about Sparta (if you haven't already). They were a fascinating people. They use to leave their children in the wilderness from the age of three. If they made it back to Sparta, they were accepted as a part of Sparta.
And kids today complain about getting too much homework...