I started off watching the anime first, which was amazing. And I admit, when I started the manga, I got lost and confused - but I still read it hoping maybe it'll fan out. It did.
In the beginning, the author is building on the characters, the techniques, and the bonds between everyone. After much battling as many shounen manga have, eventually there is an ultimatum - one event that flips everything and everyone into mad work out routines and etc. Here is where people get thrown off. Because the author babbles on about physics and the law of whatever and the past, many people, including myself, get lost. But if you just go with it, you'll realize that it's not all that chaotic. To be frank, the author is probably just rambling about it to fill up the speech bubbles, but the art itself is great.
Another thing that throws a lot of people off is the sudden Obama character and politics. Well, in every shounen, there's a bad guy trying to rule the world and then suddenly you meet new characters that band together with the protagonist to take him down. Obama is just another character aiding the take down. The fact that he's the President shows how bad the villain is and how important ATs have become. There isn't any actual politics.
Air Gear definitely isn't a manga that you would expect is easy to follow because there is just so much information on each character. Each individual has a background story that goes deeper than most other shounens. It's clear that the author consistently builds on it which makes the story compelling. However, most people will see this as a scattered storyline bouncing back and forth between the past and present.
So why did I give it an 8.5? Precisely because I am one of the readers that did get lost reading this. I do admit that the author could have organized it more fluently, but hey, I still ended up understanding it. Maybe that was his/her intentions all along, but it's a turn off if the readers don't get it.
Either way, I believe everyone who reads Air Gear or will read Air Gear should brace themselves for a rocky story. Just be assured that there is a clear plot amidst the rocky-ness.