I mainly agree with Matt's interpretation of the movie, which is actually much more interesting for its homoeroticism than for any political content. If my choices for interpretive box were "gay snuff porn" and "complex political allegory," I'd definitely choose the former. Indeed, i think it's fairly interesting that the producers and studio were comfortable with a major action flick that was so laced with homosexual undertones. It wasn't like anyone missed it in the editing phase. Clearly, there was a decision made that American society could handle this sort of thing, which either says something good about increased tolerance or something specific about tolerance for a sort of hypermasculine homoeroticism.
That said, there was a really awkward attack on the realist tradition which the movie could have done without. Also, Weigel's rundown of who's allegorically who is pretty great, though you'd sort of have to see the movie to get it, and I'd add the caveat that this is how an American neocon would interpret it:
Sparta = Israel.
Leonidas = Ariel Sharon.
Dilios = Marty Peretz.
Xerxes = Mahmoud Ahmedinijad.
Xerxes' bad negotiators = Hamas.
The Arcadians = USA!
The leprous priest guys = the UN.
Officer McNulty = France?
The giant troll guy = Saddam.
The Immortals = the Republican Guard.
The giant troll guy, by the way, is clearly the American Left. Remember: They're not just anti-war, they're on the other side!
Update: I hadn't realized quite how true to life the film was.