From what I saw in the trailer, it says it's what, 100 years after the Aang saga? The fact that it sorta looks like a modern city and I'm pretty sure I saw a motorcycle, kinda turns me off. Someone convince me otherwise-I just watched the 4-part ending of the Aang saga and it was amazing.
What does the setting matter? It's got the same mood and spirit as the original show did, and technological revolutions are fairly reasonable -
70 years is a long time, think of our own industrial revolution. Considering the whole fleets of iron ships the Fie Nation had (do you know how much infrastructure it took to build *one* iron-clad ship, let alone hundreds or even thousands?), not to mention all their other technology (huge land-train that could travel over any terrain, a preposterously massive drill, zeppelins, etc), it would have been more strange for them not to have things like cars and phones by this time.
Don't forget the fact that they've got metal bending, now.