I was disturbed by the advertising, wether that was to hide the twist or not though I'm not sure. Could just be Disney targeting too narrow an audience. The advertising does sum up the first act of the story though, as baseline as it is. The set up and reveil of the twist and everything afterwards though was absolutely fantastic.
So after getting into a shouting match with her Mom over an arranged marriage <font color=#ffffff>and tearing a tapestry her mom made for her, Merida rides her horse into the woods she's used many times for archery practice. There, she stumbles onto a witch who gives her a potion to change her fate, or more specifically, her Mom. This, in a really interesting twist, turns the Mom into <font color=#ffffff>a bear; for which her husband is known for hunting after a demon one chewed his leg clean off. So Merida and her <font color=#ffffff>now bear Mom escape into the woods to try to fix everything lending them time to bond as the more wilderness savvy Merida helps he Mom cope with her situation.
They get a clue left by the witch that explains how to break the curse<font color=#ffffff>, mend the rip caused by pride, and learn that the spell was used once before <font color=#ffffff>on an old king whom became the demon bear. Eventually, the rest of the castle spot the <font color=#ffffff>bear mom and Merida has to convince them to stop before they kill her and try to break the curse. This leads to a climatic battle <font color=#ffffff>with the demon bear and the eventual breaking of the curse.
The movie has it's Disney/Pixar flair that you come to expect, in some places more then others to the point where you'd swear this was a joke pulled from some other studio. Which I'll allow Pixar the occasional mulligan.
It's well worth it for the scenery, mythos, and the latter portions of the film.
I think what drags it down in many people is the first act, for which elements may carry over into the second and third, but the latter half certainly makes up for it in my opinion.