I thought I was utterly alone on this, or that it was something no one talked about but everyone knew. After mentioning it on the hive workshop though, dr.supergood had never heard of it; which means it must be unheard of.
If you are experiencing extreme lag while on the terrain editor, placing units, making regions, ect. Yeh know, the "physical" editor part; you may be able to fix it with the click of a button. If you notice that the simple act of moving your mouse around the editor screen is causing earth-shattering lag (For me, dropping from 200 FPS to 0, literally 0) you can go into your mouse pointer options in your control panel; and enable a mouse tail.
Not sure how, what, or why... But by enabling a mouse tail (and there may be some REAL fix for this as well) my FPS will stay at 200 while i drag units all over the screen, place them, scroll around, rotate, you name it. No more mouse caused lag!