Plot: Dances With Wolves...in Vietnam...IN THE FUTURE! IN 3D! Also, The Matrix (biological network cables) and Star Wars (biological The Force).
Characters: I liked the fact that the main guy was crippled. It added some depth to it. But come on. You're supposed to be the guy who saves the planet, and yet from the start you can't follow a simple order from a trained professional doctor like "Please sit down on the table after your brain has jumped to a completely new body. We would really appreciate it."
"NO WAY! I GOTZ ME SOME LEGS NOW! GOTTA GO PLAY BASKETBALL! OUTTA MY WAY!"
I would ship that guy back home in a heartbeat.
And Sigourney Weaver. What the hell? I thought she'd be really good, but her whole role felt phoned in.
"Where's my cigarettes? I got me some more Aliens to kill. Or save. Whatever. Where's my paycheck?"
Colors: Like, all of 'em, man. They were, like...everywhere and a part of us, man.
Actually, there were some really well done transitions when they switched from the beautiful landscapes (they truly were beautiful) to the dull-looking human areas.
Summary: As cliche as the movie itself may have been, I was still drawn to Pandora's box...I mean world. It was beautiful, clever, and fun to look at. Unfortunately, it suffered from Transformers 2 Syndrome: it was too long for a movie that focused all of its attention on effects over anything else. Sure, you may love riding The Amazing Adventures of Spiderman ride at Universal Studios, but would you really want to ride it for 2.5 hours?
The effects also don't exclude James Cameron from making a decent plot. Look at Titanic. That had pretty-to-look-at special effects with the ship and the water, AND it had a pretty good story to boot, all within a 2.5 hour time frame.
Now here's where I get to make my spiel about movies in 3D. First off, I think it's a total fad. It's not going to last forever, let alone another decade. Second, I don't know if anyone else is experiencing this, but I hate when they make certain objects pop out at you that end up being blurry because the camera is too busy focusing on something else that ISN'T in 3D. It was starting to give me a headache.
All in all, though, Avatar was exactly what I thought it would be: a theme park ride. You don't ride them and mock the poor scripts or sub-par acting. You ride them to be entertained. And I was entertained.
UPDATE: I've since written a better, more-organized rant, er, "review" that you can check out here.