Being the obsessive mega-fan of the original series that I was, I was awaiting this series as soon as the credits rolled on the original's finale.
I have to admit, it's lived up to some of my expectations. Although its definitely not Avatar: The Last Airbender, it makes a good fill-in.
That being said, it's still perfect for those who didn't watch the aforementioned.
Like the creators have said, this is like A:TLA grown up. We've still got the drama/comedy mix, but it's more for older kids/teens. There are relationships, flirting, a couple of kisses, and a love triangle, but is completely chaste, and not so "icky" that it keeps boys from watching.
There's also violence; some of it getting to the point of being dark and downright scary. On one particular episode, the antagonists (The Equalists), take control of a social hub, electrocuting anyone that got in their way, blowing up portions of the building, dragging Korra and friends out of the water after they had been electrocuted, etc. We also see multiple police vehicles(both air and water) on fire and sinking in the harbor.
I don't know if it will get any worse, but that's been the most violent thus far.
Aside from that, Korra and her friends/allies are wonderful role models for both boys and girls. They teach kids to be who they really are, and to stand up for themselves and what's right.