It's a clever ploy that Blizzard's calling the World of Warcraft Starter Edition, which even includes some of the content from the game's first expansion, The Burning Crusade -- for instance, free players can create Draenei and Blood Elf characters, two races added in said expansion. Should you decide to upgrade, you can get the core game and Burning Crusade for a cool $19.99 as part of the digital World of Warcraft Battle Chest -- though you'll first have to wait for the site to stop getting Zerg rushed by newcomers. (Apologies for mixing our Blizzard metaphors.)
Already a hardened WoW veteran? There's plenty more in the update to slake your thirst -- check out WoW Insider's handy FAQ for a rundown.