I liked it.
I was looking for reasons to not like it and came up empty.

I started watching the cartoon last week and got through Book 1 before going to the movie.
There's no way M Night was going to successfully cram nearly 10 hours of story into 2 hours, but I thought he hit enough notes from Book 1.

Being media-aware, I knew not to bother with the 3D, so I was able to appreciate the FX.
I'm no acting coach, but I wasn't bothered by any of it.
I didn't think Noah/Aang was reading and I didn't notice Katara yell "we have to go" a million times.

Rotten Tomatoes has it at 8%. AV Club gave it an F.

My only beef was that it didn't get as epic as I would have liked.
In the cartoon, Aang's command of the spirits was pretty bad ass, while this was kind of limp, but it was still kind of cool.

One trend that needs to be snapped is bright white light turning red and having some kind of deep meaning. Lost tried and failed and seeing it here just brought back that bad taste.

Overall, I'm in the minority on this one.
I liked it.