Pretty effective. There was some real character progress for Tenzin and Korra in particular; they're both a lot more mature at the end of it. I'm not so happy about how Bolin-Eska turned out, since that was an emotionally abusive relationship played for laughs, and it was a mistake to do that in the first place as well as a mistake to have it resolve so amicably. Bolin never really outgrew his own immaturity here. His battle with the abductors in the arena didn't really do much beyond reinforce his Nuqtuq fantasies, and it was only by luck -- and the cowardice of one of the kidnappers -- that Bolin found out Mako was right about Varrick.
(By the way, I like how Bolin never pronounced it as "Nuqtuq, Hero of the South." It was always "Nuqtuq: Hero! OftheSouth!" Even when he was talking in more casual tones to Mako in episode 11, he still delivered it as "Hero. OftheSouth.")
Otherwise, my main disappointment is that Asami was left out of the climax. It's not really Team Avatar without her. She didn't even get a subplot.
I don't see the objection to the "kaiju"-style battle between Vaatunalaq (oh good grief I just coined a shipper label) and Spirit-Korra. It has precedent in the giant koi spirit attack at the end of A:TLA Book One. The one thing that does bug me, though, is why Unalaq targeted Republic City, a place he's shown no interest in before. Maybe it's because he's already defeated the South, and Republic City has become the cultural and political center of the world (which I suppose we now know for certain is named "Earth," judging from the dialogue in the mover).
When Jinora said her work wasn't done, I was wondering if she was going to replace Raava as the new light spirit, like Yue and the Moon Spirit, and merge with Korra herself. But I guess that would've been too close to dying and they weren't willing to take it that far with a child character. I guess that what she did was to draw the scattered energy of Raava back in, serving as a focus for it, so that it wouldn't need 10,000 years to reconstitute into Raava.
Eh, Aang lost the avatar state and all he needed was poking his scar to get it back so I doubt this loss is permanent.
Aang never lost the Avatar state. He just lost the ability to activate it, because one of his chakras was blocked by his injury. The blow to that chakra served as a sort of really forceful acupressure, unlocking it and allowing him full access to that energy inside him.
I think the loss will definitely be permanent, because that fits the thematic intent of this finale. The thrust of it was about Korra and Tenzin learning to stop trying to define themselves by their pasts and embrace who they are now. It's about finding a new way forward that isn't constrained by what came before. Even tearing down the Aang statue was symbolic of that. If they just turned around and said "Okay, Korra's back in touch with her hundreds of past lives again," that would be undermining the message of this finale. So it's not going to happen.
What I find intriguing, by the way, is that the show's idea of going forward entails
restoring the ancient connection to the spirit world, rather than abandoning the spiritual past in favor of technological modernity. From now on, high technology and mystical spirits will be equally parts of everyday life, and that's going to be an interesting and nicely non-Western approach.
Getting four episodes was a real treat. Having to wait a full week between each of these episodes would have been torture. I wonder what made them release the last two online.
Fear of piracy, perhaps? That's often the motivation for such things. Or maybe it's because the show is getting better ratings online than on TV, at least proportionally. I think we're already starting to see the merger of television and the Internet, and it won't be long before more people are watching TV online than via broadcast/cable.
By the way, I was interested in the commercials Nick.com showed during the episode. Nice to see that Nerf is marketing action toys to girls now. I guess it's inspired by
The Hunger Games and
Brave, and maybe to an extent by
Korra, but hopefully it's the first step in breaking toy companies out of the atrocious gender stereotyping they still perpetuate.