A lot of you seem to hate this episode because Zuko betrayed Katara and Iroh.

That was one of the biggest reasons why the season finale of Avatar: The Last Airbender was awesome. Other reasons why this ep ruled so much:
Azula wins, she takes over the city ruthlessly and brilliantly.
Aang decides that Katara is more important than the Avatar State, then changes his mind when Katara's under attack and then Azula stopping him at the end when we all expect him to go Avatar State and kick some butt.

This is an episode that elevated Avatar.