Also, be very careful reading the internet rumors. I read over part of the chaos warrior book, and found a couple of discrepancies between what was posted on Warseer and what the rules said.

Demon princes must have a mark; all demon princes have hatred against their "rival" deity. Tzeentch / Nurgle Hate each other and Khorne / Slanesh Hate each other. Warseer has it posted as Khorne/Tzeentch...

Anyway, wait until the new book actually gets released for detailed reviews. Chaos players really need to have a few extra spawn and demon prince models lying around to replace their characters when rolling on eye of the gods.

EDIT:

Note that a mod closed the Chaos Warrior thread on Warseer. One of the members started arguing over power levels of the army - without actually reading the book. He kind of derailed that thread. Speaking of this, I hope to get some small games against the new warriors book over the weekend. If so, I can give some feedback on what the first cut seems to be.