I haven't seen the film. I've checked out the comic. This is the problem I have with it (I mean, the basic gut problem I have with it, not the intellectual-critical problems I might have with it if I thought about it too hard.)
You know in Men In Black, where Will Smith is sitting next to a bunch of other potential Men In Black, all of them super hardcore military badasses, "THE BEST OF THE BEST OF THE BEST SIR!" and he can't help laughing at them all?
The Spartans, in 300, are those guys. A whole city full of them. And the author thinks they're really really cool.
That's the basic problem I have with 300.
People who have seen the movie tend to love it so much that it's gotta be pretty sweet in a turn-your-brain-off-and-enjoy-the-violence, hey-did-Mel-Gibson-make-this-film kinda way. So I might still enjoy it if I saw it. But that's the impression I got from the comic.