I'm somewhat disturbed about the interface changes you shared with us during the keynote and on your website. Specifically, I'm not especially happy about all those borderless buttons.
Without affordances, those visual UI elements that suggest or reinforce areas of interaction, buttons have lost a critical user engagement piece. I'm certainly not the only developer who feels this way.
You may assume that users are now long-since "trained" on iOS, that they will feel comfortable guessing where UI components are, and will "instinctively know" how to interact with them. I believe the borderless-button has gone one step too far.
I don't believe that changing the color, as you would in an email message, is enough of a visual cue for many users -- especially those with borderline visual impairments who do not yet need assisted UIs.
Please allow clear differentiation between buttons and labels to support discoverability, clarity and user deference, regardless of user training and background.
To conclude, let me offer the following quote from the New York Times write-up of "The Guts of a New Machine":
"Most people make the mistake of thinking design is what it looks like. People think it's this veneer -- that the designers are handed this box and told, 'Make it look good!' That's not what we think design is. It's not just what it looks like and feels like. Design is how it works."
Thank you for considering my bug report.
Hat tip to Michael Heilemann.