S1s main hurdle is getting used to the choppy framerate and past the initial few episodes. S2 and s3 were pretty good.
S4 though, ugh. It basically resets all the drive that was occurring and goes back to a real childlike few episodes. Couldn't stomach it.
To compare to Avatar, imagine you just watched Aang and Toph kick ass at the earth kingdom and then they go back and chill in the southern water tribe, and everything feels like the first 2 episodes again.