John Gruber, as always, offers a thoughtful and thorough take:
Last year left me with the impression that choosing the Mini meant accepting numerous trade-offs. That is no longer the case. This is the same device as the iPad Air. The only significant differences between them are size and weight.
There no longer is a main or regular or standard iPad. Last year Apple billed the Mini as “every inch an iPad”, and that was true, but it was every inch an iPad 2. This, year, it’s every inch a top-of-the-line iPad.
I’m surprised that, during the keynote when Phil Schiller announced the new Mini has the A7 + M7, it didn’t receive raucous applause from the audience. As Gruber mentions, this year’s Mini feels like it should be next year’s. That Apple was able to pull it off now, in 2013, is truly a triumph of not only engineering but of operations as well. The spec parity between the Air and Mini makes it so that the decision of which iPad to choose is essentially all a matter of preference in size.