I've been investigating this, which we call "spine locking" for the past 2, 3 years or so. Just about every aikido technique that I can thing of that has anything to do with the body itself, not just the periphery/limbs, has one version of spine lock or other in it. I have to say, I am A Fan.
KF Wang said though in the O/P that he only likes it sideways, not forward or backward (I paraphrase), and I have to disagree slightly with that. In my own expression, I enjoy great success with postural destruction of uke when I am able to get them bending to the side, but also forwards and backwards. The engagement is almost always about over when I manage to get a position where uke is "bent" at the waist in any direction -- though forwards, because this is the direction the body is designed to bend, is the most... "escapable" if I can make up a word to describe what I'm poorly trying to explain.
Personally, I find that backwards is the most efficient option, as sideways tends to get uke into my legs/feet, and I want to avoid that.... as the uke goes to the ground the options for restraints/locks/submissions open up, to be utilized as you note them.