Lot's of games that have a Mac version do not have the Mac version available on Steam (eg. In every case I've seen including L4D2, you buy the game, not a specific version of the game. Franchises that many players around the world enjoyed on their gaming consoles were usually available only on PC, with Mac gamers left behind. For years now, one of the aspects where PC users always were ahead of those of us with Macs was gaming.
