Back when I owned an iPhone 3GS I often noticed many blurry looking apps, some from small developers and some from Apple themselves (check out the Sales + Updates UISegmentedControl in the iTunes Connect app on an iPhone 3G/3GS). It wasn’t until I started noticing it in my apps that I realised exactly what the problem was. It’s caused by a UIView having it’s origin or size values containing a decimal place. For example if the origin of a view was ‘5’ then it would look crisp, but if it was shifted to ‘5.5’ then it would be blurred to make it seem half way between 5 and 6 because there’s not enough pixels to actually do this. If you are testing on the iPhone 4 then you will miss this as it has enough pixels to actually have a view sit between between the two points. The most common cause for this is setting the view’s center position.