Just Seeing this thread now, and reading all 5 pages of Technical (lol, it was funny when you mentioned how everyone was turned off by that
) I have to say, before all else, that I love the movie, definitely in the top 3 movies for me, Next to jurassic park and Star Wars ep 4.
What you guys have said about the characters being relative stereotypes is true, well, less true than other films (*cough* Batman *cough* ) as I genuinely cared about the characters and though the plot was good, if not done before. But on that note, if someone were to make Star Wars over again, but use different characters, events, planets and sprinkle some originality into the mix, it would still be considered a classic, and praised for it's improvement (minus the Han Solo) over the original. So 'I do not think that the plot was as cut-and-dried as some have made it out to be.
Also, unless you're a lunatic religious fundamentalest, a redneck, Oil magnate or corporate boss listen to the picture's ethical message: Is it right to exploit others and the environment for your own Benefit? While not preachy, the film clearly told a message about our environmentally destructive ways like the pixar film WALL-E told us to take care of what is ours. So, no complaints there.
CGI wise, the characters were slightly too smooth to be natural, but still believable if you don't actively look for such things, while the forest, unlike some have mentioned, is totally alien. Where can you find a forest like that here? actually tell me, 'cause if there is a place like that I'm making that my next stop. It's better than the original Star Trek's upsidedown plants and fake trees, better than desert, and beter than the planet-spanning Ecumopolis like Coruscant or the Citadel in Mass Effect. Again, no complaint.
For technicality (to stay in the spirit of the conversation)
1. The diverse life on Pandora probably produces air born toxin (toxin to us) that poisons organisms that breathe it in, so higher altitudes may be breatheable to Terran life like Humans. In a link on Wikipedia (not the most reliable but reliable enough), there is a page for planet/moon Pandora (this has been deleted for whatever reason) that states that a portion of the air (1-3%) is Methane, which is unpleasant and toxic to us (in quantities like that in a 1.2 thickness atmosphere that would incapacitate us and kill us in about the time stated in the movie).
2.Pandora was likely formed Farther out beyond the snow line of Alpha Centauri System (the yellow star in the binary pair, not the Farther k type orage star) and was simply caught when forming or formed by the gas giant, which was migrating inward to the 1.1 AU area (the middle Habitable zone for A Centauri). There, the planet's glaciers would melt, and the planet would Evolve life in about 100 million years, followed by the Na,vi 6 billion years later (the Centauri triple stars are older than the sun.)
3. Pandora may have a weak magnetic field by itself, but it's close orbiting Gas giant would probably have an even more powerful magnetic field than Jupiter (who's field goes halfway to Saturn and to the asteroid belt) simply because it would be easier for a larger mass Gas giant to hold onto an Earth-sized planet, which would entail a stronger field.
4. There may be more than one Habitable world in the centauri system (in real life and the fiction universe) due to the presence of two ideal life bearing stars, a class G2V (a clone of the sun) and a K1V, yellowish stars ideal for life. If we take our own solar system for example, We have 8/9 planets orbiting one star. out of those, 3 had oceans of water and one retains it (Venus was tropical but likeley lifless, Mars was cool and was likely life bearing, and Earth was-and is- a more moderate world that maintains it's oceans to the present day. 1-in-3 odds of habitability at some point. Of those three, possibly all developed life on a prmitive scale. a 1 for 1 deal. Of those, 1 certainly has abundant, multi-cellular life covering it's surface, 1 is likeley to have some sort of extremeophile bacteria, and the other is likely dead/dying (there may be aerostat bacteria that consume acid in the upper, Earth-like atmosphere of Venus) Even then, we have Titan, Enceladus, Europa, Triton, and other moons which may have liquid oceans not neccesariliy made of water, and stable comets with plentiful volatiles and reactants.
So it would seem to me likely that in a system with two spaced out stars (the two main stars arn't close together on the scale of AU's, but rather are as far away as pluto-at 5.3 billion Km and vary to about Saturn's orbit) that have relatively ideal characteristics for Earth life would have between themselves atleast 1 Earth-like planet, or Pandora-like in the film, if not 2 or 3. Always be optimistic until proven wrong guys, always 
.
So, I'm done my rant, good night. 
