Seeing as how it takes about two days to watch Avatar, I figure it's worth offering a couple comments now that we've gone and seen it.
First, know whether you want to see it in 2D or 3D. We went on a Sunday and spent $12 on tickets. Nevermind what can be done with 3D, and with several movies in preview for their own 3D debut next year, it ain't ever being any more than a gimmick at that rate. Make it an event, because it'll cost you.
Second, remember this is a James Cameron movie. If you liked Terminator despite the 'dudes' and 'no problemos', you'll love Avatar. If you liked it because of the dialogue, you'll never leave the theater. And if you thought Titanic and Aliens were extravagantly boring wannabe documentaries with no plot, well, don't even go bothering to see Avatar.
You see, I can make some fairly specific statements about Avatar without giving anything away, because you already know the movie. The Terminator has his T1/T2 split while figuring out whether the Aliens are out to get him or should be protected. The backstory is straight out of Doom and Aliens: human trans-galactic corporation sends a department to extract important resource from foreign planet. Hostiles are present. Plot development involves various attempts to provide depth and complexity to hostiles. After surviving the first hour of the movie, the audience gets to watch the actual movie they came to see.
Here's the thing. And opinions in our little group were widespread on this, but I ate this movie up. It is awesome. It needs to be released on DVD in two versions: the edited down director's cut that's just a 90-100 minute movie, taking out the extraneously long unedited/un-proofed dialog/monologuey scenes, and another that is 10 hours long in the BBC-style documentary Planet Earth. Avatar: Planet Pandora could become the best selling faux-documentary Discovery Channel/History Channel collaboration of all time.
You see, depending on who you talked to, there was either too much cheesy dialogue or not enough time spent explaining everything, the movie was either too long or there wasn't enough plot, too many preachy soliloquies, or not enough effort spent making the emotion Cameron attaches to the characters organically earned rather than artificially forced.
And perhaps that's the coolest thing about Cameron pouring his heart into this. That is precisely what's wrong with actual military misadventures of America's recent (and not so recent) past. We're schizophrenic. We can't decide if we've been at it way too long, or if the Long War is just getting started.
For both the movie and real-life, there's plenty of ground left for both prequels and sequels.