My Wallet arrived today. California poppy, it goes well with the black 12 Mini. One issue is that the case that I was using (
https://smile.amazon.co.uk/gp/product/B08DKV6ZZ4/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1 ) has a slightly raised edges on the back and although the wallet aligns with the magnets in the phone the grip is quite weak due to the edges holding the wallet slightly above the back of the case. I took the case off and the wallet fits very securely. I can slide the wallet off the phone when it is in my pocket, put it back in my pocket and it snaps into place on the back of the phone.
With the wallet on the naked phone it fits well in the hand but the phone feels quite slippy if I try and slide the wallet off while holding the phone in one hand. I think the ideal compromise would be a very thin case with grippy sides.
Cards slide in and out without issue ( I slide the wallet off the phone and push up from the slot in the rear of the wallet.
I'll give it a week, but initial feelings are ambivalent.