Lets remember, Jony organized a comprehensive system wide redesign, and pulled it off in 7 months. Of course the betas right now are still very early, they just started 7-8 months ago. I think the fact that they had something to present this soon, being as POLISHED as it is, is an incredible achievement.
There's still some loose ends to tie up of course, but I think overall what they showed in just the short amount of time Jony's had to orchestrate this is an absolute testament to his ability as a designer, and more importantly as a leader.
Only icon I really have a problem with is GameCenter (and the apps design as well). Everything else I actually like a lot. Safari I think looks great, yet that seems to be the one most people dislike.
And anyone thinking that they can't change the look of a final release from a beta, think again. Look at iOS 4 when Steve announced it, versus what shipped. The textures changed in folders and multitasking bar, the app switching animation changed, the "window lift" animation for multitasking was sped up. A lot of details changed in iOS 4. Just like I imagine will happen when iOS 7 finally releases.