During the talk about tutorials vs. dropping the player in the game blind. I recall Jeff Green's comment about Portal where he states that the first few hours of the game are a wonderful tutorial because you the player don't know it's a tutorial.

like exposition, teaching players how the game works can slow the pace down. in theory a tutorial should be entertaining and not a mere info dump putting players to sleep or confusing them like a badly written fantasy book.

*this has been captain obvious stating the obvious*