Just saw it yesterday, I give it an 8.
Very entertaining. Its main weakness was in having Achilles be the focus of the story.
That being said, I was extremely impressed with Brad's take on the character. Pretty boy Brad Pitt really sold the illusion of being a guy who can rouse an army by charging ahead of them on the battle field. Like several others on this thread, I really like how he carried himself and moved in battle.
Eric Bana's Hector was indeed the most interesting character and compelling character, and I really think some of the scenes with Brad and his love interest/prisoner should have been cut in favor of some pre-Sparta establishing scenes with Hector.
Both men were the fiercest warriors of their people, but Hector was Lawful while Achilles was Chaotic. One fought for genuine love of his country, one for glory, and the younger, prettier sibling/cousin that they would die for was a nice tie that bound them together outside of their battlefield prowess.
Achilles was careless in watching over his young cousin, and his cousin died because of it, killed by Hector. In contrast, Hector was very dilligent in watching over his young brother, keeping him alive, who then became the downfall of Achilles. I really like that aspect of the story and how it was captured on screen. It just would have been nice to have seen equal buildup of Hector's character to get even more payoff when it was all resolved.
Helen was sufficiently beautiful, even if it would have been nice if they had found a distractingly stunning actress like Kate Beckinsale, but right now all the most beautiful women in Hollywood (Beckinsale, Jessica Biel, Katie Holmes) seem to be brunettes. Diane Kruger was definitely a better choice than any known actress I can think of.
The battles were great, and the D&D geek inside me couldn't help but smile with glee at just how reminiscent Achilles, Hector, Ajax, et al seemed to be of badass Player Characters strutting their stuff in the midst of NPC class mooks. LOTR had that, but these guys had even more of the super-heroism that D&D characters tend to gravitate toward.
A mixed bag, definitely no ROTK, but significantly more impressive than the lackluster Gladiator. Looking forward to owning the DVD.