I took some notes on noteworthy changes I noticed reading up in the new book to post for my club, I might as well share them here. Take these with a grain of salt as I haven't got it down 100% yet and there may be exceptions, but here's what jumped out at me:
No Fortifications?
The first thing is, well, I don't see the Aegis Defense Line or other terrain you can take in your list anywhere. It appears from what I've read that these are now exclusively part of Stronghold Assault (which explains why they were put in that book despite already existing in the main book). This means that if you run a tournament, and don't allow Stronghold Assault, you effectively ban these things.
No More Auto-Hit for Vehicles
Vehicles are now ALWAYS WS1. This means that stationary vehicles are hit on 3's instead of automatically.
Area Terrain is gone
This is going to cause some debate, I think. Basically the book doesn't define area terrain anywhere and basically says if you are obscured by or "in" (i.e., in contact with) a piece of terrain, you get the save. This combined with Ruins always being 4+ sucks a little, as it took away some of the strategy of positioning. But I can't 100% confirm this yet, as there may be a section with more specifics that I missed.
Mysterious Terrain is by Feature, not a General thing
They have datasheets for all the GW terrain kits that aren't from Stronghold Assault in the book, and specify that some of them are mysterious and will have their own tables accordingly (such as the Aquila Lander). This means forests and rivers (both of which are absent as far as I can tell), aren't mysterious at all anymore.
New Warlord table
A fourth warlord trait table interacts exclusively with the new objective cards.
ATSKNF Nerf
The signature Space Marine rule takes a slight hit and doesn't let you make your 3-inch consolidation move anymore (though you can still do the rest after).
Jink revamp
Jink is, as already mentioned, changed a lot. It is now not "always on" and instead is more risk/reward; you can decide to jink before any to-hit rolls are made against a model with that rule, and then you get a flat 4+ cover save, but must snap fire afterward. This is pretty huge, particularly big change for bikes and skimmers.
Assault Casualties
I noticed in assault when removing casualties, you must remove models in base contact with enemies who are at the same initiative step first. This is pretty big.
Challenge Overflow
Extra wounds made during a challenge now overflow onto the other enemies, allocated to those closest to the character that is killed.
Chariot Heavy Weapon fix
There is a note about Chariots which allows their riders to fire "as if they haven't moved" which will allow the Tzeentch chariot to fire its' weapons on the move.
Templates vs. Open-topped
Vehicles which are open-topped that get hit by template weapons result in d6 randomly allocated hits to the units inside.
Zealot rule fixed
The Zealot rule has been rewritten so that it gives the same exact effects as the other rules it previously granted, but this means that things which affect those rules no longer affect Zealot.
Vehicle damage affects passengers
On any shaken, stunned, weapon destroyed, and immobilized results, passengers now have to take a leadership test. If failed they can only snap fire.
Exploding vehicles at Strength 4
When a vehicle explodes now, the radius is the same (D6 inches), but it is strength 4 AP - instead of strength 3 AP -.
Scoring
All units are scoring now, and battle brothers can ride in each other's transports (though not sure if they can be deployed in them just yet).
General Walker buff
All Walkers get the Hammer of Wrath rule, which is great news for Dreadnoughts and such. Hammer of Wrath is more specific about how the weapon rules interact with it (i.e., they never ever ever affect it). But a free extra hit for Walkers in CC is still nice.
Split Fire and Counterattack
Neither of these rules requires a leadership test any longer, which makes them much better.
The Flying MC Nerf
This one's gonna break some hearts. Flying Monstrous Creatures are no longer able to charge into assault on the same turn that they changed flight modes. This change is clearly meant to put them into "Jump MCs that sometimes can take a long trip across the board" instead of "always flying MCs that occasionally land and fight." But it will definitely cause some notable butthurt among the Daemon community.
A roll of 6 on Perils makes your Psyker go Super Saiyan
If you get Perils of the Warp and roll a 6 on the table, you take a leadership test and if passed, your psyker gets the Smash, armourbane, fleshbane rules, plus a 3+ invulnerable save, all until the next psychic phase.
Psychic Power Bonus...for Chaos?
The rules state if you generate all your powers from one table you get the primaris for free. That's great. But there is also a sidebar for "Mark of/Daemon of" psykers, which basically says you automatically know the primaris for free in your patron god's power table. Adds a lot of potency/versatility to Chaos psykers.
These are the main things that jumped out at me on my first read-through. How do I feel about all of them? Well, as always, the new edition brings sense to the unthinkable choices beforehand. I thoroughly enjoy that the Wave Serpent spam and the FMC spam lists are going to have to be less easy-mode. Looking forward to an edition where Chaos becomes very potent again, as now their "must always challenge" rule is less foolish. The Vehicle changes are going to really change the game a great deal and add a lot of value to things like Lascannons and Railguns. It's hard to predict but things are looking VERY interesting, if nothing else.
