My application will be iOS5+ and support only iPhone 4+ so the only screens it needs to work on will be retina displays.
Do I still need to use two sets of artwork or can I stick with just @2x artwork.
If your App is only for iPhone 4 and above, you can use only @2x resources. But take into account that iPad and iPad 2 are iOS 5 compatible and don't use @2x images.