I'm still on the fence a little bit after recently finishing Book 2. Maybe it's because I've seen it all before in the previous show but nothing in the second season felt like it had much of an impact, except for maybe the final episode. Sure, it's the fate of the world and everything, but all the villains were so weak. I thought Vaatu was incredibly silly and they weren't fooling anyone with pretending that Korra's uncle wasn't going to be the villain (I can't even remember his name already). At least Aman (sp?) was menacing. Hopefully this will be explained in book 3, but I'm still not seeing how Jinora was anything but a deus ex machina.
In TLA, each season had a series of 'oh snap' moments, whether it was through an awesome bit of character development or pure spectacle, a tradition that somewhat continued with Korra's book 1. I nearly bounced up and down in my seat when
and the very last scene with the villain felt like classic TLA and fittingly dark. Book 1 was a good, intense introduction to the characters but I didn't really see any development with its successor. I'm tired of the love triangles, I prefer that Aang's other children not be involved, and I'd like to see Asami's role be a little more expanded because out of Team Avatar, she's the most interesting character to me. The characters of Korra are more matured into adolescence, so maybe they're not going to get quite the strong development that TLA had, but I just wanted more than we got.
Of course, you're talking to a guy that was always a little bored during the spirit episodes of TLA, so maybe a whole season just seemed a bit excessive to me. I don't dislike
the show and will continue watching. But I think some people are too quick to gobble up anything Team Avatar without noticing some of its weak points. It's also certainly possible that I'm so blinded by my love for TLA that anything else is just going to appear inferior, but I'm okay with that.