For examples of how Apple's new UI is less usable than their old UI see: http://uxcritique.tumblr.com
I often tap things that are just rectangles and fail to realize that other rectangles are buttons.
I can't wait for "everything is flat, two-tone, and rectangular" to be replaced by whatever the next trend is. Hopefully something more useful.
Ironic note: the flat trend was really made mainstream by Microsoft when it released Windows Phone 7.
I think we went way overboard with it and the pendulum swung to far to the side of flat design. Hopefully we start moving away from super trendy flat design, much like we moved away from those crazy web 2.0 design styles.
It's easier to be the former than the latter both in terms of skill and the politics of the client relationship, and that's why there are so many "designers" and so few designers.
Most designers don't get it right because they don't have these skills, they are only artists. And because of that they don't understand why a particular design is better than another or even what their own design expresses.
To do a real design, it asks you to do a ton of research and going back and forth between art and UX. Doing brain storming to implement old and new logic elements in a fashion way.
It's like the iOS 6 it was a big step forward because it was a design: simple, expressive, and functional. The guys who created it understood all of that. Then again, Apple followed the fashion trend more than the logic and did the iOS 7 design criticized even before it was out. The problem, among its specific fashion, was that the design was so flat it was destroying UI information. Plus visual problems: sometimes the color seems to mean something but you find one red button that isn't one, sometimes the shape, sometimes the animation...
Here is an example of what a designer should do to design a UI. http://blogs.msdn.com/b/visualstudio/archive/2013/06/27/desi...