For your regular bench shooting, you will come into problems with zeroing. With the Aimpoint mounted this high, getting a consistant zero will be harder. Think of a triangle. POI (zero) is one corner. The higher you raise the optic, the longer one side gets, increasing the angle formed by the bullet path and your optic view. Now if you extend these two paths, forming an "X" at the zero, you will get a larger angle formed, so the further back you you travel from the zero the greater the variance formed. So in essence, the closer you keep the optic to the barrel, the better your zero will be at changing distances.
Now as far as tactical shooting, imageing yourself fireing from cover, let's say over a wall. With the Optic mounted that high you will have to show more of your head. You will spend more time shooting the wall than hitting your target because the optic will clear the wall way before the barrel does. I'm not even going to get into how hard it would be shooting from under a car...[:D]