Hated it. But just to be fair...
Pros: amazing special effects, action-packed, entertaining
Cons: by-the-numbers idiotic story, cliched one-dimensional characters, downright silly acting from almost every cast member, clearly engineered to make money and not for any artistic merit, geared toward kids/no real sense of any danger in the action
I was entertained, but I came away from the movie objectively aware that it was a bad movie and that I wouldn't waste any time on a second viewing. I had to see it because of all the hype, so did... and it was just a collection of amazing special effects. When Cameron did Terminator 2, he had amazing effects AND an intriguing original story AND character development AND dangerous action with real consequences. Which is why that movie is an enduring classic, and why Avatar will ultimately (just my opinion) be confined to the same dustbin as much of the "Michael Bay Era" of action movies.