This may be Korra's greatest episode and in terms of raising the stakes and action it may be the best of the whole Avatar series, right up there with Book Earth/Fire finale, it does everything completely opposite of the Spirit finale. There is no great deus ex, the premise is very simple and the plan doesn't disappoint. We had some record number of deaths this time, and Zaheer fell hard. The ending with a recovering Korra seems to echo what Air finale ought to have done, there are no more perfect endings, and there is still more to be done, even if she cannot be the one at the moment to do it. Zaheer unlocking flying was basically perfect, although they set up the fact it was his girls death as his release quite well, and had me as this oh shit moment, too bad we will probably never see that one ever happen again.
I love that the Air Nation is taking a different step, peacekeepers of the world. Jinora's ceremony was very touching and they had the good sense not to include Kai in some flashy affection of love. The Bolin learning lavabending was cool and unexpected, since we were all waiting on edge to see him do some metalbending I don't think anyone saw that one coming.
That metalbending guard though, something is up with her, I'm sure we will see more of her in the future...