I think the common problem I have with iOS7 and Office 2013 and any similar "modern" aimed UI is too much whitespace. I think in the desire to get over skeuomorphism they threw a lot of good out with the bad. Felt and leather? Sure, get rid of that. But when the buttons have no indications they /are/ buttons, they just appear as a word and nothing else, that takes my brain a bit of extra processing to figure out. There should be *something* there to anchor it as a button, to gently remind your dumb brain that it is, indeed, a pressable icon. A good UI is supposed to subtly guide your eye around what is important, these new overly minimalistic UIs sometimes miss the boat on that.