So my thoughts on the episode:
Kuvira went to return order to Ba Sing Se. She apparently succeeded, and gained the trust of the world leaders to continue her unification of the Earth Kingdom/Empire. But I have to ask, who really maintains the order and control in Ba Sing Se? My answer is the Dai Li. For example in the original series, The Last Airbender, the 'fall' of Ba Sing Se was simply due to the group switching their allegiance to serve Azula as she was the closest to the embodiment of their 'ideal' charismatic and strong leader. And the latter reveals why the Dai Li failed to maintain peace in Ba Sing Se with the death of the Earth Queen, they need the authority of a leader to creep over the walls and on the roofs of Ba Sing Se.
And now with Kuvira, it seems to me that she is expanding the Dai Li to control the entirety of Earth Kingdom/Empire. Not to mention how the Dai Li's re-education camps are nothing new in the avatar universe. Aang encountered those, as did Korra in the previous season.
And the more I think of that, the more I keep finding parallels between Kuvira and Long Feng and Azula. It is almost as if the Kuvira we are presented today is the merger of both Long Feng and Azula.
And as for Kuvira, I found this on her appearances in the previous season: http://www.youtube.com/watch?v=a2HRFc_BRSg (There are some speculation of her at the end of the video, but it is still a nice summary of her earlier appearances.)
And finally, I kind of have to wonder if Kuvira truly managed to take over Ba Sing Se. What if the Dai Li instead captured Kuvira, and brainwashed her to act and perform as their idealized leader? The Dai Li has already performed a similar feat by brainwashing Jet. This line of thought could enable her to be redeemed later, and also enable Korra to finally put an end to Avatar Kyoshi's greatest mistake, the creation of the Dai Li.