Sketch is way more developer friendly than Illustrator of Photoshop. Combined with another app called Zeplin, Designers can instantly export all interface assets and specs for developers to use.
Exactly. I'm a developer, but I try my hand desingning most of my apps. Sketch replaced Illustrator and in part Photoshop. I do all my vector graphics with it, from mockups to production assets. It's fast, easy to use and made by a small brilliant team. [Shameless plug]: I've been designing an icon every day with it: https://github.com/andreamazz/one-icon-a-day