Going in I really wanted to like this movie. But it comes down to the fact that all the CGI, movie making art and effort exist to tell a story and this one stinks. Avatar waists a gigantic collection of modern cinema resources on an unbelievably corny story densely packed with Hollywood/comic book stereotypes. Anyone with a mental age over 12 will be disappointed ( I have a suspicion, call it a conspiracy theory if you will, that the IMDb ratings have been manipulated by the films marketers).

The only memorable character is the muscled up old Colonel Quaritch a 100% over the top militarist bad guy.

An hour and a half of gee-whiz CGI and the same old cinema industry cut-paste character and story would have been tolerable -- 2hr40min too much!

If the story had been less irredeemably bad the my science issues would be chalked up to necessary suspension of disbelief and product design. However: Exactly humanoid aliens in a world with all the other vertebrates hexapod? Lower gravity but falling motions look earthlike?

I know you'll go see the film anyway but I can't recommend it. The trailer shows off the fantastic cinema technical effects. You see that you've seen all the good stuff of the film.