There's been a lot of aangst (sorry) over the transition from the animated series to live action but I think the changes are justified. For starters, they have a new audience to appeal to, that doesn't know the original, and everyone nowadays is very quick to click away from a show that bores them in the least.
So the slow burn of the original series would have been a dangerous strategy. Instead, they've pared down the story to the essentials, adding a depiction of the backstory that was only hinted at, complete with some very un-G-rated mayhem (though still within the bounds of PG-13) and dropping extraneous elements like Sokka being a jerk, which means he won't have a character arc towards less jerk-dom.
His arc is interesting anyway; how is he supposed to be a "leader" of a bunch of supernaturally powered kids when he has no powers of his own? Or even keep up? The actor playing Sokka is so perfectly suited to the character, like he just walked off the screen, Roger Rabbit style, that I don't mind the changes.
The other standout is Zuko. The actor is already investing the character with the duality that makes him so interesting throughout the story. His arc parallels Aang's. They are both exiles, dumped into a dysfunctional world with no map for navigating it.
And this approach worked. This show is #1 on Netflix's top ten, so it looks like they've got a hit on their hands.
There are some things that could be improved. Some of the kid actors have yet to learn how to en-un-ci-ate their lines and not just mumble their way through them. But I'm sure they'll get better with practice.