i am in the middle of such a dilemma right now.
i have an ipad app, that i want to convert to iphone. i can't come to a reasonable solution to "stretch" the various 1024x768 ipad graphics elements into 960x640 iphone and still make them look right.
i would like to avoid having to redo all the artwork, and have to reimport 250+ elements and change screen XY positions etc....