According to 9to5Mac, one source described iOS as "very, very flat," while another said that all the gloss, shine, and skeuomorphism of past and present designs are gone. One source even said the flattened look is somewhat akin to Microsoft's Windows Phone platform.
The challenge for Apple in keeping iOS modern is giving it an up-to-date overhaul without sacrificing the platform's simplicity, which has been a staple of iOS and a large reason why it's so popular. Those who have seen the new build say that even though it looks decidedly different, it's no more difficult to use than previous versions and doesn't have a learning curve if you're already familiar with iOS.
Why the change in appearance all of a sudden? The decision reportedly comes from Apple Senior Vice President of Industrial Design, Jonathan Ive, who recently took on an expanded roll and is now in charge of software design.