The voice acting in ATLA was really great. I wouldn't say it was anything exceptional, as I've seen my fair share of animes with good voice acting, however compared to something like the Dragonball series, which apart from the constant screaming in every episode, had pretty ok voice acting, I'd say it's pretty decent.
As for Korra, I think it's sunken a bit. I still love the voice acting and all, however I don't feel like it's really the same as it was in ATLA, and a bit like some of the voice actors aren't as experienced. Like with Korra, even though I do love her voice, I don't feel like the voice actor does as good a job as I'd want her to. Perhaps that's just because there hasn't been any parts where they have really had a chance at showing how good they are, but I don't really know.
One thing that really irked me though, was when they put Zuko's voice on a character named Iroh, on someone born years later. I mean, it kinda makes sense since he's a descendant of Zuko, however I've just gotten used to someone named Iroh having that friendly old man voice, and just hearing Zuko's voice not coming from Zuko just doesn't really feel right :<
Eek I saw the finale and I loved it. i love this series, I hope they don't cancel it, I can't wait for next season. C:
I saw somewhere that it would be called Book 2: Energy, do you guys think that's true?
I don't think there's any chance that it'll be canceled with the very well deserved popularity it has had just over this one, short season.
About the title of the next season, I have no idea. Was the first season actually called something? Either way, since the "book" in the titles from ATLA was more to point out Aang's progress in mastering all the elements, I don't really think Energy would fit very well together with it. Though if it is true, it might give us a small hint on what the next season is about, though that's not really anything to go on :/
Really looking forward to the second season though :D