Iphone 4 and 4s both have a huge resolution (960px wide on landscape) which is exactly as wide as the Theme (based on 960px grid) which is why in original design the responsive mode is almost the same as the desktop version (it maintains clear reading on most parts).
However some of you may prefer a similar responsive version then on other mobile devices. This is why we published a special style.css that makes a specific responsive design suited for Iphone 4 and 4s (responsive design for other devices is the same as in the original one). After you download the style.zip unzip it and copy the file style.css to Theme’s directory (overwriting the old style.css). To revert the changes simply copy back the original style.css or remove the last part of the css (commented as Iphone 4).
If you have any suggestions on how to improve it drop us a note and we will see what we can do.