Personally, i myself am having thoughts about the new series, and that's based on what limited info i have on it.
1. Based on what i've read about them, it really feels like they're trying to make Korra and Tenzin seem better than Aang (which doesn't seem right, considering the latter is his son). They say Korra is the opposite of Aang in personality and that Tenzin is much more serious than his father. What was wrong with Aang's personality? Plus, they show that Korra learned three elements when she was much younger than Aang who had to learn them in the course of 112 years.
2. I'm a little unsure about how to feel in regards to the show's more "Modern" city design. I guess I'm just still accustomed to the original shows' Feudalistic/Middle Ages setting. At this point, i don't see how a modern world with microphones, cars and electricity can work with the Avatar series
3. Maybe i'm just being wishful, but i wouldn't mind if a few characters and events from the original series are referenced, if only to remind people what started it all.
P.S. As someone once wrote, Aang died at an early age due to being the Iceberg in the Avatar State. But all things considered, living to your late 60's or early 70's is a feet in and of itself, as not a lot of people in that day and age lived to be that old.