Windows Phone 8.1 developer preview is release few days before. Now, my device running with WP 8.1 preview.  Overall I am very happy with this update. We are going to get many new useful features. Like : Quick settings, Start screen background image, WIFI sense, improvements in email, audio and videos apps. IE 11 with sync and private browser option. And very important thing in this update is personal assistant. which make things easier. Her name is Cortana (beta). There many other features like...