Okay, finished watching it all... some random thoughts/comments.
1) Several ppl mention that references to other people's demi-god status was left out of discussion.
I agree, I would have also enjoyed those sorts of mentionings as it would make things (like Achillies fall) even more understandable to those who do not know the back story. However, at the same time, I do have to admit, the title is "Helen of Troy" I will give the writers the benefit of the doubt and say that maybe it was a decision made to keep focus on Helen and why she was so wonderful.
2) The whole Paris choosing Aphrodite thing.
Umm - is it just me or did they only show the goddesses offering him stuff but he never actually made a decision? I gotta say that leaves SO many questions like why were the goddesses offering him these things. Even if they did not want to stick to historical epics, the least they could have done is explained why the goddesses just up and said "hey, us three people of great power are deciding to come here and give you stuff"
3) Not very accurate
As said.. but, I let it go for the sake of just seeing what they did with the movie
4) Some scenes...
The Agamemnon killing his daughter. and the rape of Helen at the end... I got sick at that last one and litterally had to stop and do something else for a bit to get it out of my mind. (but, admitedly, I have issues..

)
5) I would have enjoyed more involvement from the gods..
But, for the same reasons they didn't go into the demi-god status of others, I'll give the benefit of the doubt that this was a concious decision. I would rather they sticked with one or the other though -- either they are there with manifestation or not there but things happen where you could question it being coincidence or hand of god. For instance, the whole wind picking up thing after the sacrifice, that was subtle but no actual presense.. it could be left interpreted as coincidence or make you wonder if Artemis was really there. This countered by the manifestation of Hera, Athena, and Aphrodite... there presense left no question... I would (personal opinion) rather have had all references to the gods in the movie be either one way or the other.. not this combination...
6) Cassandra's treatment
I do think they waited too long to explain why no one was listening to Cassandra.
I mean, at the beggining, the King was ready to have his new born (first son!) tossed off a mounatin based on Cassandra's statement.
Yet, later, her words were not headed and no explaination was given.
Only sometime near the end (after the brother's death) did the Queen say that the father just assumed the fire Cassandra saw was his burning love (or was it loins

?) for Helen. Okay, that may explain it a little but what about before Helen entered the picture? Not much was offered in the way of explaining why the king paid much head to cassandra anymore....
just the way it was done, it came off as a huge change in the king (willing to kill an infant versus willing to see if they really will burn down the city)...
That's all I shall ramble for now.. have stuff I am supposed to be doing

will add more later.
Over all, not something a 10th grader should watch instead of reading the Illiad 
But, as a movie, it was enjoyable none the less.