Here is a comparison between new iPhone4 2x retina display and normal 3gs display (click to enlarge).
Its a PSD data that I made it for new iPhone4. As you see, there is quite big difference and supporting retina display is quite hard work if you are using bitmap graphics a lot.
Because user interface for TiltShift Generator is originally made with BitmapData. I have to re-make everything and it tooks almost 2days just for drawing graphics. Anyway next update for TiltShiftGen supports Retina display. It will be out in two weeks after iPhone4 release.