The FAQ for the Daemons can be found here http://uk.games-workshop.com/news/errata/3/.
Edit: With the site redesign, the link is now here.
A lot of the stuff is common sense but there are a few that even I had to re-read. Abilities of daemonic gifts DO stack, except for where the ability is the same, i.e. 3+ save and 5+ save would just be a 3+ save.
I was a bit annoyed that there is nothing the FAQ for putting a herald on a mount in a unit and how they rank up, determine ranks etc as this seems to be a fairly controversial item. It annoys me that they take the time to write a question and then put in the answer to something that is actually stated in the rule book or army book, but then seem to skip over things like above. Grrr.
Oh well, at least it came out fairly quickly, we can be grateful of that.