Yes I use it.
I have fired many thousands of rounds using it out to 400 meters.
It is taught at Gunsite.
It is taught at Frontsight.
What you need to do is sit down with a ballistics software package. Punch in the numbers and look at the trajectory for yourself. Change your zero on the computer and look at the trajectory of the bullet. You will find that for any given cartridge/load there is one best zero that will give you the flattest tranjectory which of course makes it much easier to hit things without knowing the exact distance to the target. This includes targets near and far. What you want is the zero in which the bullet doesn't rise or fall more than a certain number of inches for the greatest distance. For example, you might say that you want a zero in which the bullet never rises more than 4" above your point of aim. Once you plug in some numbers you will find a distance for your zero in which the bullet doesn't rise more than 4" and then you can see how far away before it drops greater and four inches. The idea here is that you hold center of mass from zero yards out to distance "X" and the bullet will hit within an 8" ciricle (4" high or 4" low). Using that zero, particularly against humans allows you to hold center of mass at pretty much any reasonalbe distance and hit the target COM without having to estimate range.
Once you get done playing around with the software, you will use the IBZ and be confident that it is by far the best zero for the 5.56 cartridge.
...though it looks to be dead on.
