Just making you guys aware of an issue I had with my mini.... Started to notice a very high frequency flicker on the screen. Noticeable when moving my eyes between UI elements such as icons and the dock. Would see a "shimmering" and faint black lines for a split second before my eyes adjusted. Apple swapped it out no questions asked, and the replacement is fine.
Saw this on my early iPhone 4 too.
Saw this on my early iPhone 4 too.