Saw it a few weeks ago and really enjoyed it. The battle scenes were very real looking and Brad Pitt did a decent enough job of playing Achilles. My favorite part was the emotion and depth they put into Hector. The trials of that guy made the whole movie worthwhile.
My two biggest gripes are that they make a 10+ year war appear to only last a weekend and the silly happy twist in the end.
I am not an authority on ancient Greece and have since learned of some historical inaccuracies but did not mind or notice 'em during the film.
Well, see, that's the trouble with what Hollywood does to the classics. If you ever read one of the translations of Homer (go for the prose, like W.H.D. Rouse, don't even TRY the verse, it's very difficult to understand), you'll see how deep and rich the story is.
Also, the Olympian Gods loomed very large in the Illiad. They were totally missing from this film. Their meddling was the best part of the story.