At 7.6mm in thickness and 112 grams in weight, its the thinnest and lightest phone Apple has made. The case is entirely glass and aluminum, with a much different looking back side all in metal, and a wider metal ring around the perimeter.
Choosing perhaps not to mess too much with 'perfection' (in terms of impact on the smartphone market), Ive & co. have not substantially changed the physical interaction and touch points. The perimeter ring could be about the same thickness as the iPhone4, its hard to tell from photos.
Personally I'm not in favor of the new design, although on the interface side having the wider/taller screen and more apps will be interesting to experience. There are probably tiny details that reveal themselves once in the hand of the user that make it better than 4.
Any thoughts from Core77 forum contributors, the benchmark for industrial design community-speak?