I just picked up the same combo this week for my new iPad mini 4. I have a leather SmartCase on my iPad Air 1. I love this combo so far: light, minimal, and actually improve the comfort of the mini with bare aluminum with sharp edge (the iPhone 6 is smoother and more comfortable to touch).
What is awesome about this combo is that the cover when folded back will be held strongly against the back which is a big deal for me. I found the fact that my iPad Air 1 SmartCase cover flop around when folded back really bothersome.
The only small drawback with this combo is that it does pick up lint. A leather option would be nice. I looked at leather folio options out there and virtually all of them are clunky, like binders one would put a paper notepad in. Sena Future Folio is the only exception so far. It does however looked bulkier with a card and paper slot, and I have no idea if its magnetic cover is strong enough to hold the cover when folded back.
Are there other leather option out there?