This will feel like a bigger change than iOS 7 itself.
Apple / Via apple.com
When iOS 7 becomes available for download on September 18th, a strange, unprecedented thing will begin to happen to your iPhone. In the ensuing hours and days, every single app on your phone will change. A lot of it will happen right away, as Apple's in-house apps and well-prepared developers push out their iOS 7-ready apps, but some will take longer. When it's done, you'll be left with what is essentially a completely different experience, from the homescreen all the way down.
There's been a lot of talk about what this overhaul means — especially since even tech journalists haven't had access to most of the new iOS 7 app designs (other than Apple's) — but now, for the first time, we can actually see it for ourselves (though it's a bit blurry).
In Apple's broadcast of this afternoon's event, the company gave us a quick preview of a few select third party developer apps. They purposefully flashed the image for just a moment at a distance, but the above screenshot at least offers a tease of how your favorite apps are about to evolve.