Having now seen the iPad mini I can say I'm rather impressed with it.
Compared to the competing 7" tablets, the 7.9" mini screen gives far more than that extra 35% screen realestate, particularly for browsing and for reading electronic versions of magazines.
In portrait mode there is obviously much more visable screen with more visable content on view, but in landscape mode there's more than half as much again and there isn't the need to zoom to read pages, as on the Nexus 7, which is pretty weak in this area.
I've also noticed that in real comparative reviews (not just repeating and pontificating on specs from a spec sheet), the concensus appears to be that the screen resolution spec differences aren't nearly as noticeable in practicle use, plus the Nexus screen is marked down for it's less saturated colours and poorer contrast, making it appear slightly "washed out" in appearance.
From practical experience with the Nexus tab, I'm inclined to agree with this. The iPad mini screen does look very good, even if it isn't as crystal clear as the retina screen on the bigger iPad, but at normal viewing distances it's not such an issue.
My first impression is that the mini looks to be a very attractive proposition. Justifying the extra cost over the cheaper, subsidised/loss making tablets will be a matter of personal choice, but at least you know where to go to get help and support if you have problems with it, unlike with the alternatives.