It looks like many are having significant performance issues since the most recent patching of the game in preparation for the new Cataclysm expansion. Frame rates dropping to 3-10 FPS seems to be the most common. The default hotkey for displaying your FPS is "Ctrl+R" which will display your current frame rate above the bottom skill bars in the middle of the screen. If you have much lower performance than before patch 4.0.1 I may have the fix for you!
