I admit to being a little ambivalent about putting myself forward here. However, given that 6th Edition information is raining down on us like an orbital bombardment, and that it's already infecting the old thread like a virus bomb, I think it's time, and I'm willing to be the guy who does it. Anyway, 546 pages is probably long enough for one thread, and it's time for a new one.
I'll start things rolling here with the thing everyone's looking at right now: the 6th Ed FAQ for the IG. Let's see what we've got here, for the edition changes:
-Primaris Psykers can pick main rulebook psyker powers. Unfortunately, not having the main rulebook yet, I have no idea whether or not this is useful. I will say that Nightshroud is a power I basically never used, and while Lightning Arc is okay, it's a little blah (though works well with Grenade Launcher Vets for massive S6 BS4 shooting), so access to new powers can only make the little guy more useful. I still wish he had some sort of psychic defense, though (and no, getting his head blown off by a Commissar doesn't count as psychic defense).
-They've tightened up aura effects, Orders, etc. to affect only Imperial Guard units, presumably so you don't get ridiculous things like Colonel Straken giving Furious Charge and Counterattack to a bunch of Grey Knight Paladins. Probably a good idea on GW's part, but still...
-Commissar Lord's aura is no longer optional. Unfortunate, that. And, of course, non-IG don't listen to him.
-Techpriests, as has been noted in the old thread already, can restore Hull Points. This could be really handy to stop AV14 vehicles getting glanced to death, but we'll see if this actually means the guy gets used every now and then.
-First Rank, Fire! looks to be quite scary, since it can let a big Guard blob lay down an awful lot of fire, even on the move.
-So, apparently Hydras can't shoot stuff on the ground very well. Sucks to be all the Guard commanders who bought the Forgeworld models.
Now, as to the updated FAQ:
-Nothing much new here. Sure, there were (mainly not needed) clarifications like not being able to issue Orders on opponents' turns, Bastonne counting as an Officer for Orders purposes, etc. The Psychic Mastery Level is not a surprise. Eldrad Ulthran, the Primaris Psyker ain't.
-It is worth noting that you're now required to take one of the slot-filling HQs to lead your army. Not that anyone ever took a Techpriest (or a Priest, for that matter), but the option is gone. Unfortunate that this came along just as the Techpriest arguably got a little more interesting.
Okay, that's what I've got to get the ball rolling. For the Emperor!