I've known Shyamalan was directing The Last Airbender for a long time. Here's some backstory on these movies (from M. Night's perspective anyway):
A few years back his kid was watching the cartoon on (you guessed it) Nickelodeon (thanks Hlallu), and he decided to sit down with him and watch it. After about one or two episodes he instantly fell in love with the series and actually went out and bought every season on DVD. After watching every episode extensively, he began writing a script for a movie adaptation of it, only the script hit the two hour mark when he was only a third done with the story, so he decided to turn it into three movies. Before even thinking of getting funding to make it, he sent the scripts to the creators of the show in order to get their opinion on how he did in terms of staying true to it. The creators loved the scripts. They gave him their blessing and off he went to make his movies.
Although this is a Shyamalan movie series there will be no twists. The films will stay as true to the cartoon as a live action film series can be
That being said, I'm a big fan of the series and I saw the theatrical trailer to this when I went and saw Iron Man 2. It had my mouth hanging wide open. I actually think it looks like it might just live up to what I'm hoping for in a movie adaptation of this show.