Autolayout doesn't solve all your problems in building the UI screen. The big change nowadays in all screen sizes in iOS leads to different behaviors based on screen size. To build a universal app (iPhone and iPad) at the same time, most probably you need to build to two storyboards, which means you have to put in double efforts. However, what if you have a different UI in a landscape mode, 99% percent you would write code to handle this stuff, which is painful. More painful is the iPhone 6 plus screen size, which is huge enough to hold more details than the other iPhones, where some apps have a different UI only specific for iPhone 6 plus. Check out the following two screenshots for the Calendar app in landscape mode.
Here is the screenshot in any normal iPhone:
Here is the screenshot for iPhone 6 plus...
