Nice interview indeed; thanks for sharing it, Mike. Powell is quite articulate about what he tends to do as an composer: creating a 'feeling'. And he does it well. His work on the Bourne-films is excellent; even groundbreaking to point.
Somehow, it reminds me of the approach Goldsmith used when working on Basic Instinct. Paul Verhoeven told that he would come to Jerry's studio to not only discuss the music, but also creating it. They used Jerry's computers to change a melody-line from strings to clarinet to see what would work best.
In the same vein: James Horner once did an item for Intel, promoting their new processor (the pentium, if memory serves). He discussed how technology helped him to 'morph' the sound of a trumpet into something else (I forgot what), helping him to create a new soundscape.
Computers help composers to create a broader canvas. I guess that for the most scores that are composed today, creating the canvas (and thus the soundscape) is the focus of a composer. The themes, not so much.
