I disagree... If sports games can release new games just for roster changes without being criticized then I think the L4D2 complaints ring hollow given that there are major updates, much more than I'd ever expect out of a free upgrade or expansion pack. Roster updates and team ratings, that's the kind of thing that's perfect for upgrades/expansions because it's just minor changes. All new weapons, a whole new class of weapons, a major update to the AI engine that runs the games, new characters, entirely new zombie skins and more types of special zombie? That doesn't say expansion pack to me, it says sequel.