New in Second Edition

Does there exist a document highlighting the stuff that changed between AW1E and AW2E? Or maybe just the most important differences?

If not, could we crowd-source such a list in this thread?

Stats
You can highlight Hx.

Moves
There has been a pretty sizable update to Battle moves and Seize by Force. Road War Moves were added along with a complete reimagining of vehicles. Subterfuge moves have been added. Some old moves have hold or effects on misses now, many have undergone slight text changes which may have implications on how they're used.

Playbooks
The Operator is gone, Driver underwent a substantial change. Some class moves have been tweaked. Character creation Hx was completely redone. Angel Kits were substantially updated. MaestroD was added as a base class. Prosthetics are detailed for the savvyhead, and small but significant changes can be found in the improvement lists for the playbooks.

Barter/Lifestyle
Barter moves are mostly untouched, but barter functions entirely differently then before. A number of barter is spent to pay for your lifestyle every session, rather then every month.  All classes have a built in moonlighting, but this takes place on screen and in the narrative, not triggered or handled by rolls occurring in between sessions and in downtime. This is a massive change to the tempo of the game, and helps to make scarcity and survival become real things for the player characters.

DM Tools
Many DM tools are the same, all of them are familiar, but there are new tricks and suggested aids that have overtaken old examples. Namely fronts aren't present at all, new threat mapping aid is provided, and a bunch of new threat types have been detailed with some minor updates to the classics. 

Other Stuff
More harm types are detailed.
More weapon types are detailed.
Coming back from 12 harm is done entirely differently.
Some more fun custom moves from play testers are in the back.

If you want the details for the changes, I recommend the 2nd edition book.

Yeah, the capacity to take "debilities" in order to wipe out Harm that would take you past 9:00 is no longer a thing; there are still ways to cheat death, but it's more difficult and meaningful in 2E.

The new subterfuge moves are cool, and while most of them are variations on the sort of things that good MCs would do under the 7-9 range of act under fire, it's nice to have them codified.

As Ebok stated, Hx has been re-done (it no longer requires you to go around twice). While this streamlines character creation, one very important thing has changed: you are now asking people the questions (e.g. the Hardholder's "Which of you has been with me since before?") rather than telling them. I actually like this a little bit less, because I was quite drawn to the idea that in AW1 even your character concept wasn't quite 100% your own.

I find one of the most subtle but substantive changes is in the new battle moves. The old system of the peripheral battle moves is completely removed, and while its replacement is kind of cool, I don't necessarily think that the best job has been done in the book explaining the ramifications of what being "in battle" actually means in play. I have my own opinions, of course, and there have been a couple of really good, thought-provoking threads on here that have discussed this issue.

Stats
You can highlight Hx.

I saw someone mention this in another thread and it seems like kind of a cool idea, but... the playbooks don't have the little "highlight" circle in the HX area, which makes me wonder if that was actually the intent. Do you have a page number I should look at on this?

If you want the details for the changes, I recommend the 2nd edition book.

Yeah. I probably should have mentioned: I have the book and have read through it. But a lot of it is the same and a lot else is similar. I just want to make sure I didn't miss anything others consider important.

I would really have loved a version (maybe only in PDF) that has little annotations to indicate "this part is new" or something. IDK.

Huh you're right, they playbooks don't have a little bubble for highlighting Hx. I wonder if that's something I picked up from another thread as well. Either way, having run now two games using that: It's only been awesome.

Fallen Empires has a highlight bubble for Hx, while 2nd ed doesn't. I wonder what that says about the importance of relationships when guns aren't a thing?

Or it's just oversight and you should highlight that shit anyway.