Overall, I thought it was a perfectly serviceable show. I enjoyed it, but I will probably never rewatch it - whereas I have already re-watching A:TLA once and look forward to future rewatches.
I actually cried when I first started watching Legend of Korra - because the last time we see the Gaang they are children, and now maybe a third of them are dead. I tried to tell myself that Aang and Sokka lived for decades after I last saw them, and had full lives. But all I could think of was Sokka with his nonexistent drawing skills trying to capture now long-gone happy times.
The world was so different, too. A:TLA had gotten me attached to a certain world, and now it was gone.
I thought season four was the strongest. Kuvira was a good villain. I liked Korra's difficulty in recovering from the events of season three, mentally and physically. I liked that Zhu Li got to be a person rather than a slightly skeevy plot device - although I wasn't thrilled with the wedding. Varrick was only just starting to see her as person deserving of respect, and it didn't seem like enough for wedding bells. I wish they'd gone their separate ways instead of tying the knot.
I thought Korra and Asami made for a very cute couple. I'd heard there was a GLBT relationship on the show, and I was pleased to learn it was Asami, specifically, who Korra fell for.
I wasn't really excited by the origin story of the Avatar in season two. I found it unsatisfying.