No offense but that's your opinion. Given the lack of inventory, it seems you may be in the minority as well.
The Mini is a great product that fits a need for me, the screen is not terrible and I have no need to try to justify my purchase. I'm incredibly happy with the purchase and the screen is fine. While you may think its the worst product apple released many consumers do not feel that way.
The techies or power (advanced, experienced, take your pick) users are always in the minority. No doubt, it's a mainstream product as most Apple products are these days. The fact it's flying off shelves is due to the lower price of entry.
Even forums like this have hit the mainstream in a way. It's not like it was years ago where smartphone users were mostly professionals or more hard core users. Today, you have to filter out a lot of posts wondering what color they should get for example.
Just some perspective. Quality screens have always been a want for me. The Treo 300 was my first smartphone. I jumped to the Treo 600 when it basically doubled the resolution (these were the best at the time). Apple outdid everyone with the first iphone with its amazing screen. Palm actually jumped back ahead with the Pre with its slightly sharper screen for a time (and better text rendering IMO). But the iphone 3GS was just too fast and lightyears better in other ways and kept me.
But apple went full steam ahead after that with a shocking retina iphone and even more incredible retina ipad.
In that regard, it's just hard to fall back to the Mini. Obviously i am in the minority. For those millions of mainstream users, the screen will look fine. Just like it did a few years ago. These are the same ones who bit on the bigger android phones that started out low res. Bigger screen > quality for them.
