I finally got to see this (with my two kids), and we all really liked it.
Unfortunately Nickelodeon is one of the few non-HD channels in my cable lineup, so I have to suffer through SD quality. Ugh!
Things I liked:
+ Korra herself (more aggressive version of Katara)
+ Toph's daughter, the chief of police, I see her as a reluctant future ally
+ Tenzin's kids are great comic relief and will probably continue to be so.
Things I liked less:
- The pro bending team. The two boys are very generic looking, I cannot tell them apart, nor do I know their names.
I'm looking forward to learning more about the villain(s). I like the idea someone suggested earlier that they might create weapons from pure metals not susceptible to earth bending. Chi-blocking will clearly play a large part.