This is an amazing movie and one that you really should see in a theater. I saw it in RealD 3D and it was great, IMAX 3D would probably be even better.
This history making blockbuster is the product of years of hard work by director James Cameron (of Titanic, Terminator, Alien, etc. fame). The computer graphics, art work, and sound is amazing, and you can understand how there could be a crew of over 1500 people (the credits need to list about eight people on each row). Although the exact cost of the film has not been disclosed, most experts believe that it was in excess of 300 million US dollars.
Avatar is set about 145 years in the future on the beautiful but dangerous planet of Pandora. It's main plot revolves around the struggle between humans from earth and the indigenous creatures of Pandora. I don't want to inadvertently create any type of spoiler, so I will just say that this movie has everything (except explicit sex): fantasy, action, suspense, intrigue, romance, humor. While the premise of the movie (and many of the details) are far fetched, the story and its visuals suck you into its magical world.
Although some of the principle cast members are not huge names (Sam Worthington, Zoe Saldana, Michelle Rodriguez), you can bet their careers will be enhanced by this film. Sigourney Weaver is probably the most notable big name actor / actress in the film.
I seldom go to the movie theater (except to see almost anything with Angelina Jolie, Brad Pitt, or Clint Eastwood). However, everybody has been raving about Avatar. Leo Laporte pushed me over the edge and convinced me to get up early and go to a matinée. Again, let me implore you: Don't wait for this to come to DVD or cable, go see it in a theater. Even if you don't like it as much as I did, you will probably be able to understand what all the fuss is about.