Screenshot/Apple
Here's what's going on:
First, there have been several reports of "ghosting" on the screen, meaning some images remain on the display even after you move on to something else. These ghost images happen if you keep a black and white image on your iPad's display for too long. Developer Marco Arment created this test to see if your iPad's screen is affected.
The second issue is that the iPad Mini's display can't show as many colors as the new iPad Air and some other tablets like the Nexus 7. In his review of the tablet, Anand Lal Shimpi first discovered that the iPad Mini is missing sRGB, which is a technical term for displays that can show a lot of colors.
For many people, neither of these issues will be a huge deal. It's still not clear if the ghosting problem affects all new iPad Minis or just a portion of them. But if you do have a problem, you can return your iPad to Apple for a replacement.
The sRGB thing is a different story. It's not so much an error on Apple's part as it is an omission. You'd have to look at the iPad Air and iPad Mini next to each other to notice a difference in the way the two devices show colors.
The iPad Mini with Retina display went on sale last week. It starts at $399 and has the same super-fast processor found in the the iPad Air and iPhone 5S.