Infantry lists are going to be viable. With the ability to add things like Defilers, Helbrutes, and Fiends, you can run a Chaoszilla list now. Add in cultists for cheap meatshields and screen units.
The 'unlockable' troops thing is in, so I can use my characters to do themed lists. Ahriman is mastery level 4, and Chaos has access to it's own 'disciplines' for psychic powers, each corresponding to a particular god. Chosen are the unlockable for Abaddon, so no Abaddonwing or whatever with Terminators.
Daemon Princes cost quite a bit more, have WS 9 and Init 8, and giving them wings makes them a Flying Monstrous Creature. If you get Dark Apotheosis on the boon table, you can have as many Daemon Princes as champions if you're incredibly lucky (not likely).
Warlord traits aren't anything to get real excited about, they're comparable to the existing ones with a little Chaos flavor. Ability to infiltrate D3 units is useful.
The biggest mechanic that is going to affect stuff is mandatory challenges. Any champion MUST issue challenges (even cultist champions) which is fun and fluffy, but is going to play into how you want to deploy and assault, I think. Abaddon and Kharn are 'duh' choices to do this with. If you win the challenge, you get to roll on the boon chart - sort of a similar mechanic to the Dark Eldar Pain tokens - the more carnage you wreak, the more powerful your dudes become. The Phil Kelly influence shows here a little bit, I think.
Marks are mainly the same, but Daemon 'animosity' is back for anything like a Daemon Prince. Possessed have a D3 table that you roll for ONLY for close combat AFAIK, and are all beneficial.
Veterans of the Long War gives you Hatred (Space Marines) - to hit re-rolls in first round of CC (Berzerkers!) and +1 to Ld - I think this puts the cost back up to 16 pts, which is basically what it was before for the same profile.
That's as far as I've gotten so far. Game wise, I think I can build some competitive lists, using Forgefiends and Heldrakes for more fire support, and running Defilers more as close combat monsters. Chosen are worth looking at, for the variety of weapons loadouts you can take.
The only new models I have bought so far have been the Dark Vengeance set (giving me a power-armor 'lord' that can probably also fill in as an aspiring champion, 20 cultists, the somewhat useless but cool looking Helbrute, and some CC kitted Chosen), and the new Raptors/Warp Talons kit. I'm building them as Raptors, since I've always liked the concept, but not the funky old metal models. The new models are much improved, and use the same 'slicing' technique as the DV models, so they go together in more dynamic poses.
The wargear section does a good job of allowing a lot of customization without being totally ridiculous like the 3rd edition codex. Chaos is still very limited in the number of vehicles it can take, and the only assault vehilde is the Land Raider...meaning points wise, I'm going to be looking at the fiends and other stuff for some CC punch aside from my troops. Looks like I'm going to have to develop a 'wave assault strategy", throw the big stuff and the expendables out first, and then come in with my heavy hitters to bat cleanup.
Oh, and it has taken less than 24 hours, but already it seems (according to forum trolls) we have a 'broken' ability with the Dimensional Key and no-scatter deep striking for every unit that deep strikes after it is activated. You have to kill a model in close combat to use it, however. It also makes all terrain difficult AND dangerous near the bearer. All for the cost of a power fist! I don't think this is any more broken than any of the abilities that the Necrons or Grey Knights have though.
The challenge with this army going forward is how to synergize (buzzword alert) all of the boons, traits, marks, wargear, and special rules and abilities into a working whole. Can it be done? I think so. Will it take a few weeks of reading the codex cover to cover and playing some games? Sure.
The book itself is awesome, full color, great fluff, and great illustration. Worth $50? Debatable, but you guys can look forward to your codex updates when they come around, the production values are really good. There's a fold out reference chart that has nearly everything (boons, psychics, stats) in the back. The quality of the book fits well with my collection of Black Crusade role-playing books, with lots of lavish details.
I'm making these printable 'cards' using business card cardstock on my printer, so I can keep track of boons and traits and such. Overall, I'm looking forward to giving the new rules a try, and will probably make up a list using as much of the new stuff as possible to see how it works, and then tweak it for at least one competitive build and a fluff build. The biggest problem? Determining if I want to do Black Legion or experiment with another Legion as far as a paint scheme - I've already painted my Helbrute in Word Bearers livery, and I can't make up my mind if I want to do Iron Warriors, Alpha Legion, Night Lords, or what. I might even make up a Chaos warband for once. Ah, decisions, decisions.
I'll try to put up a post about the Chaos specific psychic powers next.