With the new iOS7 and increasing number of app interfaces using flat design, there’s no doubt that the flat trend is here to stay. “Flat” UI refers to design that uses elements without gradients, ornaments or effects such as shadows or shading.
A strong antithesis to the web-2.0 style which uses glossy, glass-like interfaces and heavy drop shadow, the flat style has received some criticism for being oversimplified and unpolished.
The argument in support of flat UI design is that it retains honesty to the materials. Rather than mimicking real-life objects such as leather, metal and fabric, flat design does not imitate something that it is not. An app interface is digital and not made of glass, plastic or fabric, so there is no need to trick the user into thinking it is something tactile and three-dimensional.
The removal of excess details and ornaments places focus on the content rather than the interface. Typography and simplified icons become more prominent as indicators of visual hierarchy rather than artificial 3D effects.
More than a fleeting design trend, the flat UI trend is based on user experience and content organization. Love it or hate it, expect more mobile and web apps to continue the flat trend.