Max Rudberg with a great article on how you should be thinking about updating the look and feel of your app for iOS 7. One of the key phrases from just about every UI based session last week at WWDC was the phrase "edge to edge content" and while all of these tips are good, I think that's the one Apple wants us to really take to heart.
Quick work by Geoff Teehan on getting an updated version of his excellent PSD template for iOS UI (iPhone only at the moment, naturally) out there. He recommends reading the new HIG before getting started on mocking stuff up and I would completely agree with that advice, it's more than just a visual change that has taken place on iOS UI design.
iOS 7 is so much more than new icons, but as the icons are the first thing that you see it's no wonder they are getting all the attention. Ian Storm Taylor takes a good look at some of the more interesting design choices with the content of the new squircles and offers some suggestions for improvement. I'm sure that the icons will be one of the places we do see some changes between beta 1 and final release so I am not too concerned at the moment.