I'm not sold here on this one. Since we know the specific small set of resolutions on iOS devices, I'd rather have a designer/UX lay down exactly how it should look, then have devs execute on that. If dev provides a valid reason why a design component would be a royal pain, then design can go back and adjust.
Just had this argument 20 minutes ago on using a native control versus designing our own and adding a few listeners - which has a better look and experience.
Background: taught a PSD to HTML college course; stopped doing PSD-HTML myself about two years ago; still favor PSD-iOS