TL:DR - It's better than the movie, but it's a REMIX. A good show in it's own way but if you were expecting a live action retelling of the orignal show, you'll be disappointed. Advise to watch it with an open mind.
Now, here's the long bit:
The show is a lot better than the movie. I'm open to new ways of story telling, however it's not very true to the original show. It's clear they were trying to make the show different from the original while keeping true to some elements. The problem being they've taken a... "unique" approach.
They've taken a lot of shortcuts with the story by taking multiple story arcs and merging them together. E.g. June and her Shirshu find Aang on Roku's Crescent Island temple..
If i compared it to the original show, here are 7 issues I had with the show (there are a lot more, but these are the bigger issues I had)
**SPOILERS FOR THE SHOW**
1) Azula's fire isn't blue. No mention of her being a prodigy in bending. In fact, later in the series she's shown to be below average and Ozai is dissapointed in her performance. She does lightning bend, but only to fire it at a building in order to prove to Ozai she can go out into the world.
2) When Aang goes into the spirit world to tallk to Hei Bai - he pulls Sokka and Katara in with him.
3) At Roku's temple, Aang finds Shyu and gets given a shortcut DIRECTLY to the sancutary with Roku's statue. No trickery by Sokka as in the original, as Sokka and Katara are being held by Koh still.
4) Roku doesn't help Aang escape the temple either. Aang walks out to find the sages paralyzed by June's Shirshu, how did she get to the island..?
5) Aang doesn't water bend until he merges with the Ocean spirit.
6) Iroh has no emotions. He always looks sad or depressed.
7) Ozai is shown by the Great Sage discover Sozin's comet is returning "soon". Seems like they're skipping season 2 considering Aang hasn't done any water bending outside of manifesting the ocean spirit yet.