"I want [something] and I want it now."
This is what I hear from reading most of those angry tweets/comments.
Sadly, sometimes they are simply shouting because the game is not what they were hyped about. Maybe we are over-hyping games to get pre-orders in? I remember a time when the first time I heard about a game was when it was actually on the store shelves (good ol' boxes). Now there are dev-blogs and the likes years before a game is actually going to release...