Pros:
Giving the idea that Korra may want to keep the metal inside of her because she may not want to be the Avatar anymore is an interesting development.
Giving Kuvira and the Earth Prince brat (forgot his name) a contrast in the way they treat everyone politically is a smart idea (even though I find the Prince irritating yet insteresting)
Toph seems to have some sort of impact on Korra. I also like how her being in this Season doesn't feel too forced at all (unlike Zuko...sort of)
Bolin seems to have finally found more purpose than being comic relief and I like his conflict with Mako
Cons:
The Earth Prince. Ugh. I really hope they do not waste potential with this guy. He is ripe for Character Development but this show seems to not be going that way at all.
(Personal Con) Saying that Korra had just abit of metal left inside of her and is making her sluggish almost made me scream "COP OUT!!!". So glad they weaved Korra's psychological state into this though but at least foreshadow this instead of making it come out of nowhere.
(Just for Fun) What's with the Doomsday device? This isn't metropolis guys.
Overall:
While this episode was slightly weaker than the ones that came before it, it gets major points for all of the Pros that it has. The Politics continue to be really great in this season and I do like the contrast between the Earth Prince and Kuvira and how they treat common people, I just don't like how they aren't doing much with the Prince. Most of the time, he's going around trying to be funny and continues to be a one-dimensional character from what I've seen through the season. And considering that the Earth Kingdom and its politics is going to be a major focus for this season and that he's getting a lot of screentime, this is entirely unacceptable.
I also like the conflict between Mako and Bolin. Bolin believes that what he is doing is paving the way to peace but Mako sees all of the pillaging going on and completely disagrees and that what he is doing is the equivalent of a tyrant. I feel that this is a pretty good conflict with a pretty decent use of politics.
I also like how Toph seems to be having some sort of impact with Korra and gives her the suggestion that she may not want the metal out of her because she doesn't want to be the Avatar anymore. Interesting psychology to bring into something that came completely out of nowhere. The metal being inside of her was not even foreshadowed (besides a few fight scenes maybe....) and you want me to buy that the metal is still inside Korra even though we clearly saw it come out in the final episode of Season 3? Yeah no.
So yeah, some pretty deep cons but overall I feel that if they fix their garbage with the Earth Prince and stop bringing up things that weren't even foreshadowed in previous season then this will be the best season of the LOK. It really has the potential to be a great season and I hope it doesn't come crashing down.
Now......to episode 4....