While funny, I doubt this is effective advertising. It won't get anyone who's not already a Penny Arcade fan interested in the game. Although, I could easily be argued that the game isn't meant to appeal to anyone who's not already familiar with the comic, so it could be a moot point.
Reports indicate that the game is
breaking early sales records, but again, I suppose that's to be expected, given the target audience. People who are likely to buy the game are the kinds of consumers who purchase games on release day. Will the game have legs? I fully expect sales to drop after the first week or two.