I've been watching some videos, and the stealth in this is looks awesome, especially the sheer variety of possible methods at your disposal, impressive stuff.
I'll admit, the lack of offline co-op is a massive downer for me. Local multiplayer is ALWAYS a priority in our house, and my brother wants to join me in this too. Online co-op with friends/family/NE will no doubt be great, but I know how much more time we'll spend on local multiplayer. Disappointing.