Who goes behind the neck for barbell military press?? If so, how far down do you go?

I have heard numerous reasons not to. I personally used to, but every now and then they would hurt my shoulders (not the good hurt) so i quit and do front military press.

is there any advantage to going behind the neck?? I want to get the most out of my shoulder workout.

And what are a couple good exercises to isolate the rear delt's? if any. I do rear DB raises sometimes, but feel that mine are lagging behind. That may just be psychological.