We're big fans of Polar, the "Instagram of quick opinions," as well as its creator and designer, Luke Wroblewski. But even a mobile designer of Wroblewski's stature (he literally wrote the book on "mobile first" design) found that redesigning a popular app for iOS 7's new look can be more perilous than it seems.
"Compare Twitter’s compose screen on iOS 6 to the one on iOS 7: the lack of strong contrast between elements makes it less immediately apparent where the primary call to action (Tweet) is located," Wroblewski cautions.