The typography looks nice - Helvetica Neue works well on devices with a retina display, though we've yet to see how it works on older devices, perhaps iOS 7 will require retina?
I'm really pleased to see they've removed some of the tasteless fake leather etc that iOS previously indulged in (compass app, games centre etc), while retaining hints of real depth and physical relations where it actually helps the design (as in the translucent keyboard). I wonder how much of that was stuff that Steve personally insisted on?
Some of the icons could do with some polish, but it's hard to redesign an entire set probably coordinating with different teams and keep them all up to the same standard - I'm sure revisions to those will come with time, and at least we've lost all that faux 3D render effect which doesn't work so well at small scale - these flatter logos are an improvement in most cases I think, though things like the photos app icon don't make sense to me. The radio and itunes icons are an example of something that works extremely well in this style though.
There are far better screenshots on this other story:
http://techcrunch.com/2013/06/10/live-blog-wwdc-2013-keynote...