1. I wonder if the four nations are still separate. I was trying to figure out which one that city belongs to, and I think it must be in the Fire Nation. It's the most likely to have electricity and airships, not to mention coastal cities with big mountains.
2. It looks about on par with the important fight scenes of the original series to me. It's hard to say what non-action scenes will look like since a trailer is obviously going to focus on action. That ship near the start was just moving in a nice, cheap, straight line, though.
3. If she's following the proper procedures, she'd have to know earth before fire, right? Isn't it water, earth, fire, then air? I'm guessing the story is set during her fire training. It would explain all the firebending action, and storywise, it would be her most trying time as Avatar, fire being water's opposite and all. More potential for her to be an underdog that way.
4. I'm not seeing the metal. If it is, that could be a real world weapon called an urumi.
5. Ayup. Though I think Aang would have busted up property, too, if he'd had the animation budget for it.
6. I'm surprised it isn't something that can fly. Two of the Avatars we knew of had flying animals. A swimmer could have made sense, too. Maybe an albatross-orca.

This is a glorified horse, not that there was ever a shortage of such things in Avatar land.
7. Might be cool if under that mask, he's someone we'd recognize. Or their son, rather, given the time that's passed.