supporting upgraded graphics

If, like me, you originally created 320x480 graphics in PhotoShop, or whatever, you will be faced with creating new graphics at the higher resolution/size. I wouldn't just enlarge them, as they will get worse, unless your originals are in something like Adobe Illustrator, in which case you can with confidence. [Damn, I wish I had done it that way.]

 

The documents related to iOS 4 are still under NDA. That said, the relevant thing to read is this section of the iPhone Application Programming Guide. It'll explain how you set views to work at a higher resolution and what you can do with files to ensure the phone loads one version of a graphic on low resolution devices and a different version on high resolution devices.