Market has been anticipating 64 bits ARM for sometimes. Finally, Apple comes out first. I am not too sure about the benefit of having 64 bits ARM on a tablet given its use. Who knows, when there is a better specification, engineers will find a way to discover its potential. Regardless of the potential of 64 bits ARM on a tablet, I am pretty sure it will benefit server, desktop and laptop computer. Given time, a full function OSX will be ported to ARM and the future generation Mac will be ARM based. The next apparent question is, "What will Intel do?"
Here in Silicon Valley, I see iPads & other tablets used quite often for taking pictures and videos, just like a huge smart phone. I may think it looks stupid, and that even a cheap camera will give better results (due to optical zoom), but apparently lots of people feel differently.
I haven't asked anyone about it, but my guess is they like the large "viewfinder" and simple operation.
I find it interesting that the iPad Air has HD video capture, but I wonder how often the camera on an iPad or any other tablet actually gets used. Perhaps it is more useful on the Mini, but it seems like a full-sized iPad is an awkward platform for photography.
I don't understand the statement about "larger Retina screen" because the iPad Air has a 9.7" screen, the same size as the iPad 4. Yes, the iPad mini now has more pixels, but also the same screen size.