In Spectrum the other week was a fabulous article on 'Pain', by Elizabeth Farrelly. She referred to C. S. Lewis' book 'The Problem of Pain', where Lewis says a few things of interest. One is that pain is essential to justice. I disagree. Undoing the benifits of wrong is the essence of justice. I think he's referring to 'the wages of sin is death'; God's judgement on the movement of man in denial of God. That's different. Death is the antithesis of God's action in creation, and represents the outcome of the rejection of God's relation with his creation. Pain results and is the great marker of a creation in crisis. To that extent, Lewis' metaphor of pain being God's megaphone telling us that we are not a-right in a life framed by our own ends, is, I think, apt.
One 'benefit' that does come from pain is that people show thier nobility in insisting by their action that (a) pain is not to be accepted, but worked against (thus the floods of aid to Haiti, etc.), because it is not a right part of our lives, but a part of things-gone-wrong, and (b) that people in the face of personal pain will often fight against it and its effects. But in and of itself, pain has nothing to commend it. It is a marker of death, and death is the last enemy which Christ has done away with.
[I seem to recall Pannenberg writing that all fear is fear of death...how close this is to fear of pain, that which motivates us to avoid it!]