For those people who think that this is going to be a mistake, do you really think Apple would change the operating system for their most important product without going through a number of variations and tests first?
There will have been a number of basic concepts developed and then sifted to a handful that went (I expect) right up to executive board level and they will have agreed on the best option before going to the next stage. It won't have been Ive beavering away in a secret room somewhere and then coming out and saying "here we are, this is it".
From a software point of view, getting a more standardised look across the OS would have been the hardest part. Once the different elements are more consistent, then future changes are easier to apply.
Like most others, I will reserve judgement until I see it myself but nothing I read here concerns me and I think it could look much better with a flat, clean and consistent style. If this goes against what Steve Jobs had as his vision of perfection then, respectfully, he was wrong because when you look at iOS critically, it is a bit of a mess and very inconsistent.