The removal of actual buttons to me seems like the most headdesk idiotic idea in the entire OS. Sorry, it doesn't matter that we've had buttons in computing for decades, they're still useful, especially when you have to actually poke at stuff on your screen to see if they do anything.
At first I thought the same thing about the lack of raised button imagery, however I think as long as they consistently use a secondary color on touchable elements such as icons, buttons, and text, people should be able to get used to it and easily recognize what is and is not interactive when it comes to the UI chrome. I am a bit apprehensive about the fact that the TabBar and ToolBar UI look so alike, but perhaps it won't be an issue for users.
Anything that gives users the feeling that they have more space rather than less without enlarging the actual device is a worthwhile goal, IMO.