I really love the series. I think the plot and animations are great, and I loved how they focused on rarer, yet truly powerful bending techniques.
However, I dislike the fact that Nickelodeon keeps trying to milk the few good shows they have by forcing more and more seasons out of the series. This prevents them from being able to work on a longer plot, and instead forces the creators to create short story arcs where the main villain is defeated within ten to fifteen episodes. Were it not for this, the creators could focus on making a better plot, since they aren't afraid of being abruptly canceled.
Honestly, I think Nickelodeon should stop trying to survive on the few good shows they have, and should instead focus on creating great shows that will truly grab their audience. At the rate they are going now, they might simply be trying to follow statistics and are failing to listen to their audience when it comes to the things their audience wants to see on television.