Brace yourselves kiddies, the japanese version is out and so is the english version of the Prima strategy guide, and I got some epic spoilers for you all. And sorry, most of it is bad.. Turn back now if you want to keep what little spoiler virginity you have left.
Alright! Lets go:
1. We have already seen ALL the weapons in the game, sorry, its 2 for Nero, 7 for Dante (counting Yamato, no Sparda, but read on)
2. We have already seen all the styles too, its 4 plus Darkslayer
3. Nero in the demo is pretty much all of Nero except the DB skills, the only new core moves you can get are 2 evasive attacks, his dropkick has to be purchased and its called "Rainbow"
4. The Devil Bringers abilities and the items which unlock them are as follows:
Evil Legacy: Mission 02---Grim Grip/Snatch
Anima Mercury: Mission 03--- Allows usage of Gyro Blades
Rusalka Corpse: Mission04--- when Nero nears secrets such as Blue Orb fragments red orb caches, secret missions the Devil Bringer will glow and make a ringing noise.
Wing talisman: Mission 05---Allows usage of red bouncing rings.
Sephirothic fruit: Mission07---Allows user to destroy tree roots blocking your path
Aegis Shield: Mission 08---Allow Nero to pick up and hold smaller enemies using them as a shield.
Key of Cronus: Mission 09---By examining or striking certain objects Nero and Dante can slow time...mostly for puzzles.
So, Quicksilver is relegated to statue activation ala GoW, and all but 2 of the DB powers are used for platforming and puzzle solving: LOL?
4. We have already seen ALL the bosses in the game, except the final final boss, who is btw, none other than Sanctus, the old guy who Dante shot in the face at the games start. He joins with the Silver Giga statue we saw (which is called "The Savior" in the game) and weilds the Sparda sword no less, but the player never gets to hold it.
(In Order)
Dante
Berial
Bael
Echidna
Angelo Credo
Angelo Agnus
Dante 2
Sanctus 1
CHANGE PLACES!!!!
Echidna
Dagon(Another Frog thing like Bael)
Berial
Angelo Agnus
The Savior
CHANGE PLACES!!!!!!!
(Berial
Dagon
Echidna
Angelo Agnus {All in the same level})
Sanctus Diabolica (or Sanctus 2)
The False Savior (or Sanctus 3)
5. STORY: Notice the "Angelo" in the boss names? Turns out Vergil himself is nowhere to be seen, the Orders powers come from the fragments of Nelo Angelos broken soul. Also, we were all right and Credo is the one winged dark knight (Angelo Credo) and Agnus is the insectoid one eyed dark knight (Angelo Agnus)
6. STORY: Glorias secret? Gloria=TRISH
7. You finish the game as Nero. Mission 1-11= Nero, 12-18= Dante, 19-20= Nero. Man, Dante lacks screen time :(
8. STORY: Nero IS Dantes half brother, at first thought BS, he is clearly referred to as a descendant of Sparda and one of the Sprada bloodline in the leaked final cutscene.
9. You cannot level styles like in DMC3, you purchase their higher levels using "proud souls" (in DMC4 there are 2 currencies, red orbs and proud souls)
10. The harder level Kob mentioned? There is a new difficulty mode entitled Hell or Hell. Basically it's the same as Heaven or Hell but you die in one hit, the enemies don't.
11. The unlockables are on the short side (Unless the guide is hiding something)
Beating Human gives you The history of DMC video, Game Clear Art: The Two Heroes and a set of 29 character images.
Beating Devil Hunter gives you all the same as above plus Game Clear Art: The cast, Son Of Sparda mode and the bloody palace.
Beating Son of Sparda mode gives you Bonus Clear Art: The Demons, 12 Publicity pictures, DMD mode, HOH mode.
Beating DMD gives you Game Clear Bonus Art: Demon Invasion, Hell and Hell mode, Super Nero and Super Dante.
HoH mode gives you Bonus Art: The ladies of DMC,
Hell and hell mode gives you Bonus art: Light from the Demon Blade.
Also, While Son Of Sparda mode is essentially hard mode there is one change. In order to progress to the next level you MUST get at least an A rank.
I can however mention here that the DMC3 Prima guide missed out the unlockable costumes also, so they might still be in there. I beleive a hooded Nero was confirmed ages ago.
12. Bloody Palace is a battle arena mode similar to the same bonus mdoe from DMC3 SE. The player battles through 101 stages, the player can choose to play it as Nero Super Nero, Dante or Super Dante in Normal or automatic mode.
When you enter enemies appear, defeat them to open a portal to the next arena. New to the palace is a time which counts down during the fight if it reaches zero it's game over. Defeating enemies gives you a small time bonus. Bonuses are also awared for clearing a stage while suffering no damage and by killing enemies with a stlyish rank.
Every 10 stages there is a boss, at stages 10, 30, 50, 70, 90 the enemies are grouped difficulty enough to be considered bosses. Stage 99 is also done in this manner. in stages 20, 40, 60, 80 and 100 you fight story bosses like Berial.
Stage 101 is Dante in quote "His most powerful and dangerous form" So I'm assuming Dted dante at 101. If you're playing as Dante you fight an evil shadow Dante (kinda like the Red Vergil I'm assuming).
13. The highest ranking is S.
Bonuses and Penalties:
No Damage--- x1.5
No Item Used--- x1.2
Gold Orb Used--- x.07
Continue Used--- x.08
Enemy Level Down (I have no idea)--- x0.8
Super Character Used--- x0.2
NO SS RUNS IN DMC4??
14. Royal Guard gets a move called Dreadnaught, which is like a DT that runs off of your Built up tension. It makes Dante invincible and impervious to knock back. His appearance also changes.
15. There is a DMC3 style end scene where you play Nero and have to defend Kyrie while teh credits roll, success gets you an extra cutscene, the contents of which are currently a mystery.
I also have full movelists for the weapons and stuff, but that will do for now I think.
GUIDE SCANS:
http://i44.photobucket.com/albums/f37/samuraisandwich/DMCGUIDE.jpg
http://i44.photobucket.com/albums/f37/samuraisandwich/DMCGUIDE2.jpg
http://i44.photobucket.com/albums/f37/samuraisandwich/DMCGUIDE3.jpg
http://i44.photobucket.com/albums/f37/samuraisandwich/DMCGUIDE4.jpg
http://i44.photobucket.com/albums/f37/samuraisandwich/DMCGUIDE5.jpg
VIDEOS:
1. Second battle with Dante, including Gloria is Trish proof.
http://www.youtube.com/watch?v=MlY_OQzZEXM&feature=user
EPIC LULZ!!!! 
On the bright side, Dante is SO badass in those scenes, and the boss battle looks awesome, even if it uses crappy repeated QTE style clashes and bland music.
But nonetheless, GLORIA=TRISH? LO FRICKEN L! DMC4 is complete. Wow.
2. Final Boss Fight Part 1
3. Final Boss Fight Part 2 http://www.youtube.com/watch?v=Kad7i99YZ78 Including Credo is OWDK and Nero is Sparda descendant proof. Warning, contains death of a DMC4 character.
4. Nero V Echidna cutscene http://www.youtube.com/watch?v=3tODRSTeAJM
5. Dantes office scene http://www.gamersyde.com/stream_6032_en.html
Well wahey, Lady mentioned Devil Arms in a storyline capacity 
wow, a while back seeing Lady, Trish and Dante in his office with the Sparda sword discussing Sparda and Devil Arms would have been a fangasm.
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FINAL NOTE PLEASE READ:
No this is not all a bad dream or cruel prank, but Prima strategy mags have a history of leaving out bits and peices, so it is POSSIBLE although extremely unlikely, there are hidden weapons or moves etc in the game. For the most part however, we all have to live with the above.
My response?
L.O.L
Ach whatever, my hype for the story and general composition died long ago following the news of Neros general existence and Dante backtracking through his levels; I am only in it for the sheer core gameplay now, and I know from the demo that DMC4 is fun to play. The fact I have seen all the weapons sucks, but it's my fault I guess, I did afterall scrutinize every available detail released over the past few months, I can't blame Capcom now I have no surprises to look forward to. I mean look at me here, in a thread I knew would remove any last hint of an unexpected element.
I can tell Capcom went way out to encorporate more puzzle and platforming focus this time. lawl at Nero getting the power to cut tree roots blocking his path, I taught that to my Bulbasaur YEARS ago 
Most of all though, I want you all to know I ****ing called it! Yay, me.
