I found this on the Blizz forums. Not sure if this is a help to those who have complained about low FPS since 3.1
[blizzard]In-game settings
16 bit color and depth options were removed from the game as a selectable feature. These were available as troubleshooting options to see if a video card was damaged. Some people were using these to push very low-end video cards to perform faster. If you need the option, try making a macro with the following text:
/console gxcolorbits 16
/console gxdepthbits 16
/console gxrestart
Pushing that macro will set the game to use 16 bit color and 16 bit depth. This setting will now save and stay that way until you use this macro:
/console gxcolorbits 24
/console gxdepthbits 24
/console gxrestart
[/blizzard]
That was definitely one of the big changes with 3.1 that affected my system's performance. I've mentioned it before, I believe.
Anyway, after using this macro, my fps in Dalaran shot from 4-8 fps to consistently over 30.
For reference, I'm using an ATI Radeon 9600 Ultra. If you've got an older card like I do, I'd suggest trying this.
Im glad it worked. I remember you mentioned something about that before so when I saw it I thought it was worth mentioning.
It doesn't seem to make any real difference on my machine...i bounce up and down b/w 3 and 23 fps in dal. Seems kinda dissappointing considering my machine was considered a gaming "powerhouse" just a year ago.