I know I'm reviving a thread that hasn't been touched in a month, but I thought I would add my own experience with the ghosting problem on the Retina iPad mini.
My dad bought one today and brought it to me to set up and test it. Basically, I use it for a week or two to make sure all is good since I know what issues to look for and how to fix them. I opened the box up, all excited because this is the first Retina iPad I have ever used outside an Apple Store or Best Buy (I went from the iPad 1, to the 2, to the original Mini) and thought the screen was amazing.
A few hours later, I left the iPad on the home screen for about a minute and a half since I was using my MBP to look something up. I hop into Safari on the iPad and I could see the home screen on the Safari webpage. I'm not talking just seeing the shapes of the icons, no, I could make out 70% of the details on the Newsstand app. It was bad. So I ran the image retention test and it came back pretty bad. I could see the check board pretty decently for ~45 seconds-1 minute. It started fading out, but it took a good 3 minutes before it was completely gone. I then went back to the home screen and I could see the Safari search bar. :/
Still debating if he should return/exchange it at Walmart (where he bought it) or go to Apple for a replacement.
By the way, its a Space Gray 16GB Retina mini for Verizon manufactured in Jan 2014 by Foxconn (I believe).