I think one has to weigh the situation and consider each case existentially. Let's say you capture someone and you know she has knowledge of where a suitcase nuke is located in a large American city, and you know she knows when it is set to detonate. I believe in that case, the end justifies the means. Our morality should never be used against us!
Shades of gray occur when you don't know if the person knows something "interesting." Or when what the person knows is of tactical relevance. I don't think I can approve of torture unless there is some sense that the captive's knowlege can save many lives.
On the battlefield, I think we should strive to operate under the terms of the Geneva conventions. I emphasize strive. Troops should be well-versed in the rules, and should be supervised and held accountable for their mistakes. The question of what accountable means would be up to a jury of their peers.
When we think about the bravery of our troops, remember, they each know that sadistic torture is waiting for them regardless of what they can supply their captors. This deepens my appreciation for their service.
In case I haven't been clear, I believe we should avoid torture under almost all circumstances. Resorting to torture for tactical reasons, especially given the fact that we're the invading army in Iraq (in this case), would be quite unforgivable. It would also pitch us off of the higher moral ground we so much need as we try to engage the population. These opposing forces are their sons and brothers.
In the end, I think we have to decide what is least distressing for our consciences.
And the woman you're torturing will tell you what you want to hear, or she'll be a hardcase and use the pain to supply a mental focus, and actually use your own torture techniques to resist interrogation, or you'll screw up and kill her, and you won't EVER get the info.