UPDATED : 1/28/08
From what it writes there (Direct copying):
-There will be Daemon Princes, but it will be a 'poor choice': fluff-wise they are despised by Daemons, being half-humans in nature (Alessio's words). It's unclear how (and if) they can be possibly worse than they are actually ... no source confirmed that they can be taken as Heavy Supports, but it is highly probable. (Duh, if DPs are weakened by a lot then what's the point for them to lead the armies?)
-HQ choices will be Greater Daemons and Heralds. Heralds will be 0-2 choice per HQ slot. Heralds cannot be attached to squads with different Marks than their own. (Better Daemonhosts?)
-Greater Daemons will be valid units (no more Independent Characters). (Meh, they're Monstrous Creatures anyway)
-Daemonic Gifts will be back again... but it is unclear which ones will come back, and if they will be available only to Heralds, or they will let you customize your Greater Daemons. (Custom GD will be cool, but they have to set limitations on taking Daemonic Gifts/one-or-anotehr choices or the gifts will flow to some standard ones like 3rdEd)
-There will be a "Daemonic Tank" as Heavy Support choice (Daemonic Engine?): it will be half-daemon/half-vehicle, born out of the wreckages of Predator, Leman Russ etc. which are left in the worlds scourged by warp storms. Alessio referred to it being the 'coolest models he has ever seen'. (see above pic) (HELLCANNON! Sorry, I didn't actually saw taht pic.)
-ALL Daemons from past editions will be playable again (I'm expecting Beasts of Nurgle and Fiends of Slaanesh!). (Great, so calvary Bloodletters anyone?)
-Daemonic Special Characters will be detailed (OK, nothing new here... I'm hoping to see Doombreed and Foulspawn again!). (Now we need someone with Dreadaxe probably)
-All Daemons will be Fearless and, not being summoned, they will NOT be instable. An 'all-daemons invasion' in Warhammer 40K occur whenever Warp Gates open and daemonic powers feast upon the innocent inhabitants of the nearby planet. (Hordes of Chaos from WHFB......Except seems stronger.)
-It will be a HTH-oriented army, though Horrors, Flamers and the new Daemonic Tank/Engine will provide a good amount of firepower. No words about the 'Unbound Defiler'... which doesn't mean, of course, that it is a fake. (Fair enough, old Daemons are just mostly CC units)
-ONLY DAEMONS in this Codex. No Lost and the Damned, no Mutants, no Cultists, no Chaos Space Marines. (Predictable)
Army composition:
HQ
Greater Daemons
Herald (2 for slot)
Elite
Flamers
Flesh hounds (w/special character)
Fiends of Slaanesh
Beast of nurgle
troop
Daemonettes (most powerfull choice)
Bloodletters
Plaguebeares
Pink Horrors (w/special charcter)
furies
nurglings
Light support
Bloodcrushers
Seekers of Slaanesh
Sreamers
Heavy supports
Soulgrinder (modified Defiler)
Daemon Prince (very customizable choice)
There are 3 special Greater Daemons ( one for Nurgle, one For Tzeentch and one Undivided) and 4 Special Herald ( one for God)
Troop abilities:
Daemonettes: fleet and rending
Bloodletters: PW and FC
Plaguebeares: FNP, Posioned Weapons, Slow and Purposeful
Horrors: Shooting one
General rule: All Daemons have Invulnerable save, can be placed in deep strike and have immunities versus Istant death
All codex entries (yes, even the Soulgrinder) are daemons.
Lord of change is very powerfull as he has some kind of force weapon, all the tzeentch gifts and shooting powers, he can shoot up to 3 times at 3 different target. IMHO the Lord of Change is the best for versatility, shooting VERY well and can kill anything with force weapon. and has a 3+ Inv. save
The Keeper is less stronger but made more attack and shoot a "Lash" like power, can Hit and Run and have assault and defensive granates, plus Fleet.
The Great Unclean One is very resiliant but sucks for initiative and powers respect the other three.
There is no daemonic weapon for normal HQ, don't know for special one.
Seekers of Slaanesh are mounted daemonettes.
Beasts of Nurgle have toughness 5 and FNP.
Icon are avaliable to the following:
Herald
Bloodletters
Daemonettes
Plaguebearers
Horrors
Bloodcrushers
Seekers
Daemon Prince
For the "we are legion" gift, it allows to shoot at two different target with different weapon. It's very expensive for troops (10 points less the then a lascannon to a Choosen CSM unit) but cheap for DP (like a flamer).
Core daemons are cheap, all unit cost less then a CSM, Daemonette and Plague less then Lesser Daemon in CSM codex
They come 5-20 unit.