L4D2 achievements spill the beans

The full list of achievements is here.

This is what they teach us:

1. The last two campaigns have been dubbed "Dead Center" and "Hard Rain."

2. The new "Realism" mode is a modifier to existing difficulty settings.

3. The game has a defibrillator that allows the Survivors to revive dead teammates.

4. Adrenaline provides the Survivors with a speed boost.

5. Suvivors can drop ammo upgrades for their teammates.

6. There's something called a "bile bomb" available to the Survivors.

7. Survivors can collect vials of Boomer bile from a specific "uncommon common" infected type. (See #6?)

8. Survivors can (somehow) "honk the noses" of the killer clown zombies.

9. The same clown zombies can lead hordes of common infected towards the Survivors.

10. There is a character with unique mechanics called "Moustachio" (presumably in Dark Carnival).

11. Dark Carnival also features and interactable garden gnome.

12. There is no spawn-pressuring. Ever.