Brought my teenage kids with me to see Avatar well aware of the hype but deliberately avoided spoilers/plot clues so that it would be a fresh experience.
Summary- we all loved it.
The plot, however is nothing new. Mix 3 parts Dances With Wolves, 2 parts Matrix, and 1 part Predator and you're good to go.
Ignore the many critics that have said that James Cameron fell flat with this one and just go- be SURE you are going to the 3D version, a 2D (traditional) version is playing as well.