[ender7]

Gradients and juicy-fruit graphics are like candy -- they provide an instant and strong positive feeling, but they don't age well. If you had to eat nothing but candy, you'd hate the sugar-coated morass your mouth had become. In general, a flat icon tends to age better and reduce "eye exhaustion" (not a physiological thing, but a psychological one). Note that this applies mostly just to icons; the entire UI is not so tightly bound by these rules.

However, design is also trend-oriented, and flat is a rising trend.

[jarrett]

> but they don't age well...In general, a flat icon tends to age better and reduce "eye exhaustion"

Two thoughts on that:

1) Is that just an opinion? (If so, there's obviously nothing wrong with that.) Or is there some objective evidence?

2) How well do icons need to age? Realistically, how many icons in the wild will go 5+ years without a design refresh?