Just saw this last week, and, well, once is probably enough.
I wanted to get the best experience so I went for that IMAX 3D dealy (a whopping 2200 yen) and I definitely was NOT disappointed visual-wise.
It's one hell of a ride that does not let off until the very end, and considering this movie is almost 3 hours long, that is an impressive feat,
In the end though, I felt really annoyed at how incredibly cookie-cutter the story is. You can seriously see the entire movie play out in your mind's eye within the first 10 minutes, and there isn't a single surprise along the way.
Characters vary from boring to annoying, the main character felt like a "Paint by numbers" drawing without the paint, Sigourney Weaver was running on automatic and the bad guy was such an incredibly bog-standard Military Dude with Contempt for Everything that it wasn't even particularly satisfying to hate him.
I guess the Na'vi were the best part of the movie, which is understandable, but even they weren't that interesting.
Some comments:
1. Would a LITTLE comic relief have hurt here and there?
2. Unobtainium is without a doubt the single dumbest name for a material EVER. Seriously, if this was a videogame, everyone would be facepalming, but because this is James Cameron it's suddenly okay.
3. Besides, what does it DO anyway? All we get to hear is that it's worth a shitload of money, and that's it. There's SO little background story.
4. I would have liked some basic explanation on the link between the Avatar and the Human Body. When the Avatar dies, what happens to the human? This was significantly explained in the Matrix, but not touched upon in Avatar, and I find it hard to care for some guy enhabiting a blue body when I know that his REAL body is safe in a machine somewhere. Once again, some BACKGROUND people!
5. I am beyond the age where I find movies that are purely about visual prowess and no originality whatsoever interesting enough to watch twice.
6. I kept thinking I was watching a videogame (albeit an insanely beautiful one), that whole Life Tree and Spirit Energy stuff reminded me of FFVII, and even the monster design looks like it belongs in an average JRPG.
So yeah, a bit too overhyped methinks.