I just saw it today. This movie is effing awesome. In EVERY way. It's a believable re-telling of the legendary tale.
(SPOILER)
Arthur - a man devoted to the Roman Army, and freedom. His pulling of "The Sword in the Stone" is actually his father's grave. He doesn't pull it because he is special, but because he tried. He wanted to save his mother from the evil Merlin, but wasn't able to. He unites Briton and becomes King.
Guinevere - a native Britoner, and a powerful warrior. She is a member of a Celtic tribe of some sort, led by Merlin. She is saved from a torture chamber run by a Roman official by Arthur, and falls in love with him. She does not share Lancelot's feelings for her.
Lancelot - He is taken from his home and turned into a Knight. A pagan, he follows Arthur, but constantly challenges his command. In the end, he is killed by a Saxon. His character is the most different from what you would think.
Merlin - Hardly Arthur's mentor and friend, for much of the film he is the leader of the Celtic tribe that attacks Arthur and his Knights. He is not a magician, but a dirty old man. Eventually, he unites with Arthur, and his savage troops help defeat the invading Saxons.
The Other Knights - there are 5 other Knights of the Round Table in the film, Gallahad, Gawain, Tristan, Bors, and Dagonet. Dagonet dies in a small battle against the Saxons, but his sacrifice won the battle for the Britons. Tristan dies in the final battle. He is killed by the Saxon leader.
The Plot - Arthur's knights come from Salmatia, which is in Eastern Europe. They are drafted into the Roman Army for 15 years of service. On the very day that their duty is supposed to end, they are sent on a mission to the north of Briton to rescue a boy who may succeed the Pope one day. While there, Arthur is forced to attack Roman officials because they have gotten a village to believe that, by ruling over the native Britons, they are doing the work of God. Arthur is a Christian and knows this isn't so. He sends the boy back to southern Briton, but takes the entire village and and flees when they learn that the Saxons are invading from the north. It is here that he meets Guinevere, who is a native Celtic that has been taught that the Romans are evil (which they are). While in hiding, Guinevere lures Merlin to Arthur's camp to work out a truce against the Saxons. Arthur denies it, because Merlin killed Arthur's mother. The group travels to a frozen lake, where the ice is thin. A small group of the Saxon army follows them. Arthur tells the villagers traveling with them to go, and the eight knights (Arthur, Lancelot, Guinevere, Gawain, Gallahad, Bors, Tristan, and Dagonet) stay and fight. Their superior bows wipes out a good portion of the 200, and Dagonet uses his axe to break the ice, though it costs him his life. The group returns to southern Briton, and the knights receive their discharges from the Army. The Saxon army comes to that town. Arthur and Guinevere are the only ones that stay and fight. However, after hearing the drums of the Saxons, the other knights return. An epic battle takes place between the Saxons and Arthur, Guinevere, the Knights, and Guinevere's people. Obviously the good guys win, but Lancelot and Tristan both die. Arthur and Guinevere are married, and Arthur is declared King of Briton. The end.