About the only things I keep turned up a little are distances are set to good and particle density as well. Too low particle density and you will not be able to see effects to avoid in dungeons and raids. I keep sun shafts and water effects off totally; they are hogs as well. Pretty much everything else is set to low. It would be nice to have everything set to ultra but with WoW's cartoonish graphics it really won't look stellar to me anyways.
Btw, I cap my fps to 30 and hardly ever experience lag. There is one 5-man instance boss effect that causes me a little momentary lag but I have yet to experience any lag in the only two 10-mans I've done, Boradin Hold and Black Wing Descent.