Quick bit of code to throw in your app delegate as a test for any missing retina assets. Useful when checking if you’re all set for the retina iPad:

// Figure out which images don't have an @2x
NSArray* files = [[NSBundle mainBundle]
    pathsForResourcesOfType:@"png" inDirectory:nil];
for (NSString* file in files) {
    if ([file rangeOfString:@"@2x"].length==0) {
        NSString* retina = [file
            stringByReplacingOccurrencesOfString:@".png"
            withString:@"@2x.png"];
        if (![files containsObject:retina]) {
            NSLog(@"Missing retina: %@", [file lastPathComponent]);
        }
    }
}

Thanks for reading! And if you want to get in touch, I'd love to hear from you: chris.hulbert at gmail.