Let's be honest.
It's not bad, but it isn't good either.
The acting of some of the kids can be improved, then again what can you expect... the same thing happened with the Harry Potter movies.
The costumes, on the other hand, need some serious re-designs. Everything is too bright. Too clean.
Other than that, I am giving four stars solely because I want this show to succeed, I want to see the actors grow into their characters, and I want the PR team to actually listen to fans and make necessary changes. ATLA is one of the greatest animated series of all time, and this live-action needs to do some justice to that.