The gore is no worse than in ROOst and that had no problems with the Australian ratings board. It's also significantly less than many other games that get through just fine, so there is very little chance of us getting a shafted version here (Australia).
Incidentally, the censorship was the sole reason that I refused to purchase L4D2. Even with the crazy sales, I will not pay money for a cut down version of a game (and on a random side note, I also won't pay money to Activision for any game at all because, well, because they're Activision).
Personally, I think the explicit nature of the gore and the rather stressful and inescapable atmosphere of the combat in RO is what makes it psychologically affecting enough to make me genuinely distressed by the idea of real violence.
I've never understood the social practice of censoring extreme violence. You can't understand something like, say, the Holocaust without seeing the genuine outcome of it.
To butter over violence and make it into some cartoony caricature, in my opinion, is what makes it so much more of a delight than the true horror that it is.
I think the change in public opinion between World War 2....which contained some of the most garish mass-bombing campaigns in human history, and Vietnam indicates that the transmission of real images of combat instead of the cartoon caricatures and heroic wartime propaganda, fireplace stories of combat heroism and Captain America comics is far, far more effective a deterrent to actual violence.
Of course, videogames are a far cry from genuine war footage, but they can try. And they should. Anything less is disingenuous.
