Make no mistake -- I liked the film (and I haven't read the comic, by the way, as any geek should) but the philosophy behind 300 is disturbing. Of course Frank Miller has always leaned towards the darker side of humanity, from RoboCop to Sin City to his recent take on Batman ("I'm the god-damned Batman") among other things.
I've not talking about the violence in the movie. That's expected and warranted. It's the ultra-masochism that viewers embrace during those two hours. It's the alpha male -- the male who relishes in combat, the man who's not supposed to show any weakness, the father who is supposed to kill his child if he has any flaws, the father who abandons his child into the wild. In today's modern world, it would be perceived as cruelty (although that is us applying our social norms on another culture). And perhaps at the end of the day, how King Leonidas doesn't show the same attitude towards his son (or at least it wasn't shown in the movie).
Another point of contention is the extreme subjectiveness of the battle (demonic enemies, superhuman opponents) but in a way that's to be expected, at least to gain viewer sympathy for the under-dogs that is Sparta. Some blogs I've read also reacted to the historical inaccuracy (and how the war was eventually won by the Athenian navy) but that's probably in the same area as the subjectiveness of the film.
Maybe it's because I've only heard guys's opinion on it but the scene with the Queen's sacrifice admittedly disturbed me (and others) although in a sense it shouldn't. She's still alive, after all. Her reputation tarnished but nothing she won't survive (and didn't redeem). Again, it's probably pressing my alpha male buttons where the worst thing that can happen to you is what happens to your wife. I wonder how the opposite sex felt about that scene.
But the thing is, it works. It all works. The audience was engrossed. It wasn't just a suspension of disbelief but of moral norms. Didn't we movie-goers embrace the Spartan ideal? Or perhaps it merely awakened the slumbering beast within us that despite the "compassion" we've nurtured in the past few centuries, there's a part of us that wants to embrace the culture and belief of our ancestors (and in fact as a kid I did witness this attitude, where to cry is to show weakness, to fight is to prove that one is strong, and where beauty is equated with morality).