Flat designs are seen everywhere. Personally, I do not like that the important role of colours seems to be ignored, but I appreciate the focus on clarity and content.
When iOS 7 was revealed, the reception was ambiguous: Some claimed that the graphical style was just a copy of Windows Phone’s, other claimed that Apple just took the good parts and improved them, following the general trend of flat design.
This post of Niclas Hellberg illustrates that the icon design of iOS 7 is inconsistent. Personally, I think that Apple just could not make a 1:1 copy of a competitor’s design, thus having to create an own style. The colour palette is consistent, after all.
Microsoft has received wide attention for their new design if Windows 8 / Windows Phone 8. Some say the design brings along much more clarity, which is true in a certain way, but I personally believe that the opposite is the case. A realistic logo might be harder to recognise at first glance, but once you got used to it, it was very easy to find on the UI. Now on Windows 8, colour does not have a meaning any more and any colour coding that worked before is not useless. I guess people will take longer to find the icon they search for.