Ok. I hated this movie. I almost walked out, but I was with three other people. I didn't read every single one of the responses in this thread so forgive me for addressing some things that have already been mentioned, and I will do my best not to include any spoilers.
I'm a huge fan of the animated series. Huge by saying that I think its one of the best shows on television I've ever watched. I wouldn't say that I'm a fan boy only because I don't go crazy over lore or even remember everything that happened in the whole series but I will admit that I cried several times watching the series and I grew incredibly attached to some of the characters.
I could go on and on about every single thing that I thought was wrong with it, but as I saw here some people mentioned, those are like, end of the spectrum huge fan goes nuts because appa's face didn't look as cute as it should have, or the firebending from the source issue (still think this is stupid but I'm not harboring any grudge over that). With any movie adaptation a director and writer are going to take creative liberty, I get that, but I think he just went too far. Ok - from here on in there might be a small spoiler, if anyone has an issue with them please let me know I'll edit the post.
For one - changing the name pronunciation.
I don't buy the excuse of "actual dialect this is how you say it". This is the airbender world - a fictional world where there IS NO ACTUAL WAY to say it. While the influence of asian culture is obvious, so is the fact that everything is fictional - made up. On top of that, names are more than just names, they are part of what attaches us to a character. Our ears are trained to hear "aang" and "sokka" not "ahng" and "souka". That audio training helped to grow and influence our attachment to that character. The second you take away that familiarity, the second people have to start re-thinking who they are watching. Is that really going to be OUR Aang, or does new Ahng have some new personality traits? Understand what I'm saying? While this might be completely irrelevant to anyone who is watching this show for the first time, you are losing quite a bit of the initial feeling for the character that fans have from the very start. Imagine if they changed Harry Potter's name to Henry Potter just because "Harry" is not a proper English name (for illustrative purposes). Imagine if they called Hogwarts Hugeworms because warts seemed to be too offensive. That would not fly.
I'm also irritated at the complete absence of certain characters - won't tell you which for those of you who haven't seen it yet, but it hurt, and I am just really upset about that, because there were two in particular that SHOULD HAVE DEFINITELY BEEN IN THE MOVIE. On top of that, where are all the animals that live in the airbender's world? Where are the koalaotters that live in the North Pole? We got a glimpse of ... I forget the name of the firebender transportation animals, but they had about three seconds on screen. One of the most charming aspects of that show was the creativity released in the flora and fauna - including some spirit world inhabitants, and NONE of them were there. This made the world a bit more detached for me.
The race card didn't really bother me too much, except for the fact that it seemed that Sokka and Kitara were the only white people from the south pole. Way to use a bunch of eskimo looking extras and stick some white people in there like a damned sore thumb. Unbelievable.
I hated who played Ozai - what a pansy - he acted well but he was NOT the right person for the job. Ok, thats nit-picking too.
Earthbending. What the hell? Its hard for me again to go into detail without spoiling a scene.
Lastly, the plot. Yes, the plot.
I am not so ignorant as to think that certain parts of the season would be left out entirely, that is going to happen with anything, ever, hands down. However, there were a few incredibly important plot points (in my mind at least) that were left out, and could have been added. I don't want to hear that it would have made the movie too long. If a bunch of brats can sit through a three and a half hour harry potter movie they can sit through a three hour avatar movie. Taking the short cut not only left out some shit that should have gone down (I don't care what you say), but it led to some of the plot being rewritten, enough for me to think "what the hell?". It kept out a lot of the character development, something which probably would have made the movie much better. I didn't care about a single person in that movie (SO two dimensional) and keeping in some of the action that happened in the season may have created more room for the viewer to actually begin to care about the characters and see them grow and change in their own ways. Sokka and Kitara were two of the most boring people I've ever seen on screen, when in the show they are two very dynamic personalities that really pull the entire story together.
The end of the movie was the biggest let down for me.
And if I'm not mistaken, Avatar Kiyoshi was a boy.
Yeah, sorry, but he murdered it.
Why I liked it a little though - it was visually beautiful. The bending action scenes (EXCEPT for earth bending) were incredible. I loved how the benders actually looked like they were using their body force to make things happen. I liked everything about the actor who played Aang except for when he opened his mouth. I did get the chills in several parts. But as a whole, I'm pretty sure that M. Night should jump off a cliff. I think that Nickelodeon should hire someone else to make the movie, start all over. Pretend this shit never happened. What has been seen cannot be unseen.