The Legend Of Korra is a very worthy successor of the first series. It's a totally different environment, and the circumstances are also entirely different, but you can see that the makers of the series have put a lot of work and effort in the second series. The only downside I can think of is that, because the series will only concludes two seasons, is that, in my opinion, everything's a bit rushed. It's like they want to fit a lot of content into the 2 season time-frame. On the other hand, the series is brilliantly detailed, just like its predecessor, and has it's typical quirky humour. And the tension that they're building up throughout the show is an excellent way of keeping people tethered to their screens and to the series!