World of Warcraft Hardware Performance Guide
 

While World of Warcraft players might not need the 100 frames per second that serious Counter-Strike: Source players demand, the game still challenges the PC system hard enough to warrant a hardware performance upgrade guide. Even though we can get away with lower frame rates in the massively multiplayer online role-playing game environment without losing competitiveness, it's still nice to stay above 40fps in Azeroth. Before we get to the actual test results, we have to note the way in which we tested. Given the online, persistent-world nature of World of Warcraft, creating a demo with a series of consistently reproducible events is exceedingly difficult, if not impossible. Simply going out and slaying the same wolf again and again wouldn't cut it, as other characters and monsters may appear on and off the screen--even the day and night cycle will change the way a scene is rendered from moment to moment

http://hardware.gamespot.com/Story-ST-x-1304-9-9-x