The Kobos have been unboxed and while the girls were doing their homework I set it up for them and loaded their books onto it (using Calibre and saving to disk since Calibre doesn't recognize the new devices yet.)
I can't get over how small it is, but then I'm used to 6" eReaders. I remember thinking the same thing when I first saw the Sony 5" eReaders.
First impressions - it's a great little device. The interface is similar to the Touch - if you have the 2.1.1 firmware, the layout of the top bar on the home screen looks like that with the addition of the home button on the top left. Under the mosaic the three menu items are Library, Find Books and Reading Life. The Wishlist is a panel across the bottom of the screen, but I don't know if images would show there (they don't have wish lists) or if it's just a link that launches the wish list on the store. I imagine that when the Touch firmware is updated we'll get that as well.
It has shelves. I'd love to be able to add books to a shelf from the library, but if this functionality is coming, it's still not here. Page turns are fast, as is the return to the home screen. I didn't get a chance to look at the fonts or compare the screen to my Touch - the Minis were whisked away by eager hands before I remembered I wanted to do that.
All in all, I'd give it a thumbs up. If you like the Kobo Touch, you'll like the Mini.
ETA: Davidfor, if I get my hands on the devices again later, I'll try the Calibre detection you outlined..